It's similar to riding on an airplane and the oxygen masks come down. You are supposed to put yours on first before trying to help your children or other passengers. To be succesful in life and society, one needs to maintain at least a certain level self maintenance.
First off, most mental health or mental wellness issues are temporary and manageable. There is often someone out there having a harder time than you. This also changes constantly for most situations. However, there are people that have to live life with certain problems or factors. I learned Hunter Safety, or Gun Safety from a man that was missing both legs and a hand from a grenade explosion.
There is no one-size-fits-all solution to happiness. Everyone is at a different stage of their life, their observations, their experiences, their regrets, and their lessons learned.
Growing up, I was taught to try and do acts of kindness / favors / "good turns" when possible. This was the motto for Scouts (I didn't do Tiger Scouts, but I did Wolf Scouts, Bear Scouts, and one year of Boy Scouts). I also learned this in Christianity, which I grew up going to church as a Methodist at the Salida Methodist Church. I made this YouTube playlist to explain my thoughts on Religion and Politics: The Two Taboos