Over-depending on a relationship to make you happy is the same as prematurely planning your own funeral - it's not a good idea.
Take a quick inventory of other areas of your life and ask yourself if you feel fulfilled in those areas, independent of your romantic relationship: social life with friends, career, extracurricular activities or hobbies, and charity. Why the last one? The best way to help yourself is to help somebody else.
Ultimately, if you're focusing too much on your relationship, the odds are that you are simultaneously neglecting another area of your life.