Do something that tu enjoy for a happiness lift,or the best thing to do would be to tackle whatever's making tu stressed head on. If tu leave a problem,it won't go away,it'll only get worse over time so it's best to solve it quickly before it makes tu even más stressed.
go for a walk, listen to music, have a long bath, write in your diary, watch a funny film, read,draw,go on a shopping spree,eat chocolate lol..anything tu enjoy doing.. :)