Surround yourself with positive people and try to have minimum contact with negative people. The more you surround yourself with positive people; it will help you to see best in yourself and others. Negative people will just make you more depress and you won’t be able to appreciate the things that you already have.
The question about minimum human contact made me wonder if a person could suffer any of the effects if they saw people outside of their cell /constantly/ but was never interacted with. even with an animal(s), plenty of room to move, entertainment like books and things, decent or even high quality necessities (food, drink, bathroom, etc), but no one talking to them even even though (they think) they can be seen and heard by all people outside.