How not to become too attached?

Thanks for reading this,

Anyways, I have a question for you all, how not to get too attached to someone. In the past, I became really attached to a girl, thought she was "the one", then for one reason or another, we broke off, and I fell like crap for several months afterwords. What are some ways, other than dating multiple people (sorry-don't agree with that), that I can do to prevent myself from getting too emotionally hooked on a girl? I am dating one now, and have found that one way is to not talk to her for several days on end, and to let her somewhat "chase" me. I am just afraid of being hurt really badly again, I need some advice. Thank you.