What to do to prolong a relationship?

Hello I'm Oscar and I have received quite a few insightful answers for my past questions. I have a very bad habit of getting attached too quickly. I fell madly in love with my first girlfriend and thought that the world was covered with honey and roses. Well it was cheesy and lovely, first love attitude, with the conclusion coming to I poured out everything and ended up being way too attached and needy. the break up follows with her liking to hang out with her friends more

Now I'm in a new relationship, and I swear I didn't like the girl as much at first. But only first 5 months I grow completely attached to her and I am scared something similar will happen again. I don't know what to do. I try to act not attach, i guess the only way is to put my mind onto other things. Yes im very insecure answers from experienced are prefered.