How did it happen.

Thanks, managed resolved it, I chat with that sim along with happy text when my simself in happy mode, the red bar when down, keep on chatting on computer and red bar goes down. 

 Not sure how my simself and that sim person fell, cos I was playing other Sims, when they start falling out and fighting. 

And wonder about this Simself it mean me as in the Sims but half different to me and what I do in real life.

I agree with the above.  I had teens who graduated early and went to university together. (Had them in the same dorm so I could control them both.) He was a very successful young Rock Star, Global Superstar already and of course fans would often approach him even on campus. Being teens, however, she got very miffed with him giving attention to anyone other than her. (Teen mindset, go figure.) I was devasted because these two were meant to marry after graduation and they were failing rather rapidly. (I am really annoyed at just how fast relationships deteriorate in this iteration of the Sims.)  I had to use the above cheat to get this couple back on an even keel, so to speak. It worked.  Best of luck to you.