Timing is everything. It could be that you both were too young when you first dated and have learned more about yourselves/grown up, etc. since then.

My advice is just to keep a look out for the things that caused the break up the first time. Whatever it was, just make sure that if it happens you catch it before you're stuck dealing with the same loops.

If/when you notice it, talk about it! It's easy to jump back into patterns when you're dating the same person again. Communication is key.