I don't know what kind of troubles you may face in your life, but I know you will face troubles. I don't know in what ways your heart will break, but break it will, time and time again. As much as I'd like to tell you what to do to protect you from troubles and heart ache, you probably won't even listen. Even if you did, I would rob you from life lessons that will help you grow as a person. Nothing like first hand experience to teach you more about yourself and the world around you. What I can do is try and make sure you don't go through all that pain for nothing. The price of pain may be high but it could give you valuable insights, if only you allow yourself to recognize that.
Even though you do not yet have 'the' successful relationship, you still have multiple deep, meaningful relationships with so many others in your life and they teach you a lot about yourself, too. In order to have 'the' healthy, happy, sustainable relationship we all deserve, we need to be well adjusted adults within ourselves with good, healthy relationships with those around us. Invest your time, energy and emotions in those relationships which you do have; the ones that enrich your life, the ones that surprise you, the ones that teach you more about the world and yourself. In a way, they are a prerequisite to being able to find a good life partner. In time, and after kissing a lot of fucking frogs, you will eventually find a frog that doesn't leave as bad an after taste as the others and live in peace knowing you will never have to experience that horrid after taste ever again.