When you allow yourself to change the focus of your happyness to be another persons happyness, it's a way deviate attention from your own failures and feel accomplished no matter what happens to you personally. The major problem is when you lose that other person, it leaves you without objectives, and shakes your entire existence, leaving the sense of emptyness and being lost.
Finding your focus is what should matter the most, make yourself and your personal accomplishments your objectives and that will be the most important step in finding your own path.
Sounds easy... It's not.