i had the same problem for a while
the best thing to do is sort out what ever is making you feel bad in your life
cuz its way easier to just be happy than to try be happy
but while your in the process of sorting shit out
a found the woo method really helped although it sometimes didnt always maintain through out the time i was out
see
YouTube - RSD's Tim vs Jeffy (Woo vs Non-Woo)
and there is some links from there
its all about getting your energy levels high and increasing positivity
by shouting wooh!
the time i was out
luck !
piece!