How do you accept that this is your life?

Lately I've been realizing something about myself. I'm always looking forward to the next thing, the next place, the next person. I can never just be content with where I am, who I'm with, or what I'm doing. I can't just be "in the moment" and enjoy that moment. I know that I do this, but I can't seem to make a change in myself or my thinking. I want to enjoy my life, not keep looking forward to "someday". Any suggestions, tips, personal triumphs?