I am afraid of becoming emotionally attached to this girl?

So I have a wonderful girlfriend who I love spending time with. However, I have had few girlfriends in the past and got connected with them emotionally and it caused a great deal of chaos. I met this girl and we are madly falling for each other. I love this but who knows? She might lose interest one day and dump me, or something beyond both of our controls will occur and we will be separated? I fear these things. It will end in pain if these things happen. How do I make sure I don't get hurt?