While you shouldn’t focus on the past, you should focus on the future, at least somewhat. Of course, you don’t need to (and probably shouldn’t) ask how many kids they want before the salad course arrives on date #1, but you don’t want to wait until after one year of dating to find out that they never want to get married if marriage is a non-negotiable for you. It’s not always fun to talk about things like life goals, religion, marriage, politics, etc., but naturally work your deal-breakers into the conversation to make sure you’re at least on the same page, as soon as you start to see a future together. Also, whether you’re looking for a long-term relationship or are looking for more of a casual fling, communicate it.
My father often reminded me with his examples how difficult it is to forget the past. I believe that he has a good point. But I also believe that I can get around his mistakes if I use online dating. There are a lot of people here and I will never be bored. I can communicate with several in a row but choose the one who is most pleasant.