Not trying to create a pity-party or be all woeful, but to answer your question:
My source of stress is highly contextual, but fundamentally the common denominator would be a sense of insecurity.
I feel a sense of financial stress due to not being financially secure. I have taken proper measures to ensure I am on the proper path to financial security, but it seems like one job loss, one major medical emergency, major market crash, etc., is all it takes to wipe it all out. Not to mention all the rising costs of everything too.
I have occupational stresses (software engineer) due to my incompetence, lack of useful/meaningful skills, poor knowledge of fundamentals (my comp sci program was so poor that we almost lost our accreditation), etc.. I've basically been a junior developer for the last 7 years.
Couple all that with my various issues, and yeah, I live in a perpetual state of stress and anxiety which creates a not so wonderful negative-feedback loop.
I've tried therapy, psychiatry, etc., but any solution is like trying to put out a forest fire with a garden hose. So, when nothing else works, all I have left is escapism. Luckily, I do not have an issue with any hard substances.
However, one of my biggest crutches and forms of escapism are video games. The sad reality of why they are so appealing to me is that these games create a world that is more appealing than the current one I live. In the real world, I have no meaningful accomplishments, nothing to be proud of, etc.. In games, goals and objectives are clearly laid out, easily obtainable, and if I fail to achieve something I know that I am the sole reason -- not some variable out of my control (no office politics or BS).
I have a chance to not be below-average for once, and when I manage to accomplish something, it creates a sense of fulfillment and accomplishment that I cannot find in the "real world." When playing competitive games, my contributions actually matter, and if I do well, my teammates express a genuine sense of appreciation and gratitude. They relied on me, and I pulled my weight/extra-weight. It sometimes feels so good.
I know it is all just a false sense of well-being, for any sense of accomplishment I feel is quickly fleeting. At the end of the day, when I turn the games off, what am I left with? I didn't really accomplish anything tangible -- no real skills -- and in the real world, none of it matters one bit.
It seems that I have managed to lose the ability to put forth any effort in bettering myself, and I am just in some kind of going with motions and distracting myself anyway I can.
So yeah, sorry for my long ramblings, but it felt good to get it out.