I got caught up first means that you were sidetracked or taken away from what you originally set out to do or planned. So, to get caught up in the moment is to be sidetracked or taken away because of some specific event. An example, I was supposed to study tonight, but my friend and I were hanging out and I got caught up in the moment. Remember John that you have to study tomorrow, so when you start to watch tv, don´t get caught up in the moment. I hope these two examples help. Let me know if you have any questions.

"To get caught up in the moment means to be carried away by the emotions at the time and to act irrationally" Here there are 6 other meanings of "catch up". It is a useful site. http://www.thefreedictionary.com/get+caught+up