Your first priority should be taking care of yourself. Remember the plane safety demonstration? You always put your own mask on first, even if it seems selfish.
You're in the best position to help others and make good decisions when you feel stability in your own life. Making sure you'll be around a long time also makes you last longer as a resource to society, and to your family.
You can't do any of those things you mentioned if you're dead, sick, or miserable.
I don't buy that 100%. At some point you will get old and sick enough that you risk becoming a huge resource drain. It may sound heartless but I am saying it imagining myself in that position and saying no to millions of dollars in medical treatment for a few more months/years of misery and pulling the plug instead. The benefit for my kids/family would be huge.
Then look at it like this: the better you take care of yourself, the less likely you are to have a severely degraded quality of life before your luck (or health) runs out.
Lives are long and pass through many phases. We will all be dead, sick, or miserable someday, and one hopes we will be cared for as we cared for others and taught them to care.
You're in the best position to help others and make good decisions when you feel stability in your own life. Making sure you'll be around a long time also makes you last longer as a resource to society, and to your family.
You can't do any of those things you mentioned if you're dead, sick, or miserable.