I think a lot of it is that we as a society only portray beautiful young people as being happy and successful. It doesn't matter if you travel the world if in all the pictures you're old and fat. Our stories of someone going on an adventure to achieve their dreams all portray young people. Then after that is just happily ever after. We don't often see films about some 43 year old fulfilling a lifelong dream to climb a huge mountain, even though that happens all the time. Your dreams will be just as great if you accomplish them when you have wrinkles. And you will be just as happy getting married now as you will be 3 years from now when you've lost 50 lbs.

Challenge your internalized notions of what a happy successful person looks like. Most of them aren't 25.