Like so many people, you don't have the best opinion of yourself. What you don't realize is that the way you have lived your life so far was actually the best you could have done. If you "missed" opportunities, it was in your cards to miss them. You may believe that you ego-self of body-awareness is in charge of your life, but not so. You have a higher aspect (your higher self) that never sleeps, even if you do, that never lets you down, even if you think it does, that never makes mistakes, even if you think you do. What you call mistakes is actually nothing but your inner guidance. Mistakes provide you with the opportunity to unfold you potential, challenge you to tackle your fears and insecurities, and get you in "touch" with guilt and shame for other "wrongdoings" in any past lives of yours.
When you compare yourself with other "normal" people, you are bound to end up being frustrated with your life. Having many relationships doesn't mean anything when one doesn't have a happy relationship with onself. If you can be happy and content with being alone, by or with yourself, you can also be the same with others. Just having many relationships doesn't automatically mean one is happy. In fact, having a strong need for relationships in life will make someone hand over his power to others, and will end up causing emotional attachments and expectations. There is a time for everything, for being alone and reflective, and being social and out there. Accept what you have right now as ideal, for it has been arranged by your higher self for a good reaon. There are no lost times because the only time that exists is right now. The past is with you always, right now. You have the choice to see your past as regretful, and this will make your present moment to regretful also. Or you can choose to see your past as one that has been as good as it could have possibly been, given your karmic lessons, and this will make your present moment ideal also.
Make your life your teacher an honor each part of it, especially the negative things. The more you accept your weaknesses and mistakes, the more you will seem them as blessings (in disguise) and derive great benefits from them. I suggest that you read Lifting the Veil of Duality - You Guide to Living Without Judgment (www.ener-chi.com). It will help you see your life for what it really is and help you live a more fulfilling life through conscious choicemaking.

Blessings,
Andreas