If you like your spirituality to be a deep cosmology without superstition, and your mental health practice seasoned with logic, close observation of your own thinking, and a non-fanatical social outlook, you could do worse than studying Buddhism. Besides, there's no reason to 'give up' a theistic religion for Buddhism. If you approach the non-magical side of Buddhist practice, you can still be, as many Buddhist practitioners are, Christian, Jewish, Islamic--whatever.
My own favorite commentator and translator is the Vietnamese Zen Master (and poet and artist) Thich Nhat Hanh, whom his followers fondly call "Thay," a Vietnamese term variously pronounced "Tie" or "Tay" as nationality dictates perhaps, meaning "Rabbi, Teacher, Maestro"-- that kind of title. But you can sample from perhaps hundreds of writers and lecturers and leaders. What's important, I think, is to differentiate between the psychological/philosophical practice and the religious beliefs and rituals. I know many Buddhist teachers and practitioners think that you "MUST" believe in spirits, deities, gods, demons and magical formulas and rituals. Most of all, the most common non-rational tenet is reincarnation.
I can't say any of that is wrong. It's just that, to quote an apocryphal remark of LaPlace to Napoleon, "I have no need of that hypothesis." Somewhere (it's written) that when Buddha was asked by one of his students whether or not there was life after death, he responded in the same vein: his teachings were not invitations to speculate about invisible and immaterial theories. His teachings were how to practice supreme and sublime sanity. Yes, such practice can and must become, to some extent, psychedelic: i.e., we can all agree rationally that everything is connected to everything else, but when you grasp it deeply, it is said to "make you one with everything." At that point life and death are no more separate than you and the air you breathe. It is said.
YOU ARE NOT YOURSELF ALONE
Buddhism, overall, is a system of thought and behavior directed toward reducing suffering--suffering in and of one's self as a direct result of and cause of suffering in "the world." For if you can grasp deeply and intuitively that within-the-self and outside-the-self is a false dichotomy, you see that every action is an action in the world sum of suffering and delight. The "self" as a being delimited by the boundary of the skin then becomes an illusion.
Buddhism is inherently consistent with a common First-Americans' belief that the earth is our body, its rivers our blood, its air our life. Buddhism agrees. Agrees literally. No single thing exists entire and to itself alone. Thay calls the realization of this mutually dependent web of being "Interbeing" as an equivalent of the more complex Buddhist phrase "Interdependent Co-Arising." "This is because that is. And vice-versa. Not just a causation through time, a causation through space. Interbeing.
Louise Erdrich wrote that the Ojibwe word "Manitou" does not name a 'primitive god,' but is the reverent word for that mystery in which all things have their being. Not primitive at all, but much more comprehensive than most Christians' idea of "God."
Mental health? No such thing as one person's mental state in isolation. So your path to personal 'salvation' has to be via an effort for everyone's salvation, everyone's happiness. Compassion for all, the self included. Salvation, or 'Enlightenment,' thus cannot be achieved by someone in isolation, because there really is no isolation except a delusion of separateness.
NOTHING IN THE COSMOS IS PERMANENT
All human suffering springs from that delusion, and its twin: the desire to make things last. To oppose death, to oppose change, to try to build up a store of things that are yours unchangingly and forever. Illusion of permanence. Illusion of separateness. When/if you read or hear about Impermanence in Buddhism and Emptiness, those words refer to the antonyms of humans' desires to make things last, and their delusion of separateness. There is no separate self. That separate self is 'empty' as a concept.
So there's no contradiction between spiritual practice and social practice. Christ put it like this: "Even as you do to the least of these, so you do to me." Or, as he died, tormented by Roman guards, he said, "Forgive them. They know not what they do." They don't know that I am one with them and so they languish in ignorance and suffering.
The marks of spiritual and mental health are generosity, compassion, stability, happiness and peacefulness, and stability--equanimity. These are not considered to be 'feelings' but character traits that come with deep meditation, especially on one's own thoughts. They are not virtues, as in good behavior that can affect one's value or worth. The compassionate person is more fortunate that the selfish person, but not "better." There is no hierarchy in practical Buddhism, Zen Buddhism. And maybe the hardest habit for a contemporary American to break is the habit of perceiving everything by comparison in a hierarchy: good and evil, worst and best, least and most, superior and inferior.
There are degrees of freedom from suffering. That's it. So if I feel compassion for others who are suffering, it may break my heart but it will not contribute to the world's suffering. I may grieve for the destruction of the web of life through pollution, waste, greed. But I do not increase my suffering.
To grieve, to know what one's pain is, is to be free of it becoming a permanent knot in my guts, anger in my mind.
Of course if one holds the goal of decreasing suffering in the world, it's easy to see that compassion is a useful tool. But it is not a virtue that makes me or you better. It's not "praiseworthy" so much as it is plain good sense. In that connection I remember an episode of the "Friends" tv series in which Joey and Phoebe try to find how they can do a good deed that doesn't benefit themselves. They find it impossible. I miss Joey and Phoebe.
To perceive reality with good sense, one must be capable of good sense. Good sense requires a mind that can hold focus and can separate itself from waves of mental chatter and tsunamis of emotions.
To achieve a focussed mind, one must train it not to chase after every whim nor wobble with every moodshift, whim and fancy. Mind-training. Who or what can train a mind?
FOCUS ON BREATH TO TRAIN YOUR MIND
As in theatre training, the first available physical tool is awareness of breathing. Instead of worrying about the lines or the audience, turn your attention to the physical sensations of simple breathing. As you experience breath, the mind is given something practical to do that helps it escape nonsense. The actor may indeed experience breathing with an increased vitality. That increased vitality could become nervousness if the mind was given over to looking at it and describing it and worrying about it. But that increased vitality is mere excitation: it is the same physical sensation as preparation for receiving a football pass, as playing music, entering a stage, or focusing on deep contemplation of what the mind is.
It's intense. Intensely alive, deeply alert, enlivened. It is a discovery mode.
The practice of conscious attention to breath helps a person to locate 'home base,' from which they can see how the will-o'the-wisps and mirages sweep over the surface of the mind like reflections of clouds in a lake. You don't stop the clouds. You just don't obsess about them and mistake their transience of the deep inner silence of the water.
Meditation can be as simple as that. Training the mind to know itself. Quieting the ideas of passion and finding the physical site of feelings. Once you can 'feel' your feeling, it can pass. You don't have to keep complaining about it to yourself. You feel your feeling, you cradle it as if it were a distressed child or whimpering puppy. And it calms down.
The mind matters. More on that later.