It's frankly ridiculous to assume that any relationship is good, or has the potential to be good. The opposite is also true. If you were to marry each person you ever met, you may find your true love several times, but it would never be a good relationship.
It's survival of the fittest. If you want to survive, you have to be fit. That means eating right and exercising. But you should only work out if you are being healthy for yourself. True love is based around what is inside a person - not physical beauty. And the only way to show people who you really are inside is to change so you're not so different from others. As long as you don't change who you really are, and are only changing for yourself, you are sure to find true love.
That some people don't get this is mind-blowing. So no, not everyone deserves a relationship, but if you really wanted a relationship you would get one. Just work hard and be who you really are.