Simplified answer: you need to experience positive emotions day after day, so the positive memories would balance negative memories.
Don't get stoned out of your mind, that doesn't help.
Take a little, see how you feel, find the right dosage that make you smile or laught easily, try to keep up with that dosage for up to 5 days.
Make a 5 days break, more, if you can, repeat.
You will get somehow lasting effect.
I didn't try many strains (doing my first grow), so far the best strain that made me feel happy was Gorilla Skittlez, but I didn't like that it made me hungry.
I am going to grow Jack Herer next if I won't find anything with better effects.