The reason so many people find it so hard to be happy is that they will always see the past better than it was, the present worse than it is, and the future less resolved than it will be.
Keeping a positive outlook is one of the hardest challenges to overcome, but is crucial in the pursuit of anyone's happiness. We will all face difficult times in our lives, but the truest test besides overcoming these obstacles, is how much we may let the challenge bring us down. Of course it is best to not let your circumstances weigh you down at all, and it is also best to keep a smile on your face, along with the most positive attitude possible. This is way easier said than done, but is very possible.