For example, being single and hanging out with someone that you would like to be with and their significant other. On paper, what' s the big deal? You are hanging out with friends. Emotionally, every time he touches her and picks her over you it breaks your heart a little. Why would you do that to yourself?
Or, talking with your ex on the phone in front of your boyfriend or husband. Intellectually, no problem; we are all adults here. After all he said he did not have a problem with it. And besides it's Christmas. At the emotional level, he hears you laugh and sees you smile- and then worries that you still like your ex more and are not fully over him. He trusts you a little less. Meanwhile, your ex starts thinking there is still hope of getting back together. I hope that little "harmless call" was worth it.
The fact is we often underestimate the emotional impact that experiences will have. At the emotional level, we may not be as cool and secure as we think we are. We set ourselves and the people that we care about up for a lot of unnecessary grief. It affects our ability to trust ourselves and each other.
So, upon considering an experience, try getting out of your head and asking yourself, "How will it will affect you and the others involved emotionally?" Use this "emotional consideration" as a factor in making your decisions. Remember... emotions often do not make sense intellectually, but they are more directly correlated to our happiness than anything else.