Why do I always feel like I'm waiting for something?

I am a person whose happiness is fleeting. I know I should be happy because I have so much to be thankful for, but alot of the time I'm not. I never feel truly satisfied, and if I do it's short lived. I have plenty hobbies and friends, boyfriend but I always feel unsettled in myself and feel like I give, give, give. I work hard, treat people well. Why do I feel this way? Anyone else ever feel like this? Life just seems to be going in circles. I am anxious that I will spend the next 60 years going in circles.