Tafflaff,
there are a number of things you can do to help yourself, right now though it's 2am here in australia on new years day so i'm exhausted & having trouble seeing much less advising so i'll just give you a couple of suggestions.
First nothing worthwhile happens overnight & without some effort from you.
Second, smile :d whenever you see yourself in the mirror smile (trust me think about how you feel when you smile, do it this instant!! Didn't that feel good?? & if it didn't you just need to practise!!

), you should also get in some extra practise by smiling when you say hullo to anyone, that includes greeting your family with a smile (i know the welsh are supposed to be a dour lot, but be unique!!

).
Third, try & take an early morning walk (it will be easier after winter, but a gentle bit of peaceful exercise will help).
Fourth post again & remind me to continue, but start the remedy now!!
:d

:p

:d