How To Do it? - How to Pretend to Be Happy?

I'm not happy, should I just pretend I'm happy? I don't know how to do that. Oh God! Is it my fault? Or I'm just not grateful enough? Or I really really need to get my 'muscle' pumping to get to my ideal life. What's my actions? What's my choices? I need to set my mind. I need to really get going, or I'll loose this battle.