When you meet someone for the first time and your eyes lock and you feel that spark, you climb on your emotional fence and say "Hmmmmmm". The difference between the upside and downside is not the feeing. The difference is asking yourself some questions before you leap. Now you can still leap fairly quickly if you have learned some assessment skills.
In my life, I have built an emotional fence that allows me some distance to be able to gain some perspective. Now I will be the first to admit that when that great feeling hits, it is very hard to have perspective. Some perspective is better than no perspective. So what do I mean? Try to look at the person from their point of view and not your point of view.