I miss… well I miss me

I don't ask for much, at least, I think I don't. I'm not asking for the world, just a teeny bit of luck to come my way. I miss being the way I used to be, cheerful, optimistic, bubbly. I miss being happy. Yeah I smile and laugh along with everyone else but, I don't always feel it inside. Some days I do, some days I actually feel like I'm getting better and happier, then it all goes downhill again and I don't know what to do. I just feel miserable and easily annoyed, I can tell that my friends are getting bored of that side of me but there's nothing I can do, I'm sorry.
I wish I knew how to get better again :/