You life is like a story. You are the author and you will decide how the plot goes. Sometimes, you get writer's block or you mess up so you need to fix your mistake with a big pink eraser. Everyone in your life are just characters, they all come and go but they are important to the plot.
When you fall in love with someone , it's like you get a co-writer. You have someone that will help make decisions and tell you when you're doing something wrong. The only difference is, you don't get to decide if there's a happy ending.