"He is a wise man who does not grieve for the things which he has not, but rejoices for those which he has." Epictetus
If I could give you just one piece of advice. One tip that could dissolve your worries and concerns, that could change your life, then it would be this.
Be grateful for what you have. Be grateful for the simple things. To have shelter, food, clean water and loved ones. There are many people who don't.
Gratitude is like a healing balm. Apply it daily and your quality of life will improve dramatically. Anger, depression, stress, regret can not survive when gratitude is present.