It's not less rewarding but I can agree, more exhausting.
Religion doesn't make sense to me either really, but stepping on other people to gain material wealth would not feel rewarding.
Can you maybe be more specific about how you want to be good in the world and let a little bit of the other stuff slide? You can't fix everything, and remember YOU are also a person you should be good to. Being selfless is hurting at least one person.
If you need medication to sleep and feel ok, there's probably something going on with your mental health. Not anything to do with whether you are "good" or "bad" just something to tackle so you can function in your life.