I've read so many books - academic and mainstream - about how to be happy and achieve stuff... they all boil down to the same four principles.
1) Treat and speak to others as you wish to be treated. (don't be a self-obsessed, self consumed c***)
2) Don't hang around with people who secretly or explicitly hate you / jealous of you and want to bring you down - you CANNOT fix them - and they delight in hurting you.
3) Don't blame other people for your shi*t. Work out what YOU got wrong, do better.*
*Unless you are actually a baby. Then it's fine.
4) Drink coffee, keep dancing / keep socialising
There is a fifth in my opinion. Care for animals. Even picking up shit is therapeutic.