After a while, it hit me: this strategy made me deeply unhappy.
With time I observed a lot my mental process, mood and behavior, and I noticed that things like being rude, cheating, being selfish, etc. while paying off on the short run, were affecting my long time happiness.
Apparently I was not made for that.
Lying, is one of those things. I can lie. I'm actually a very good lier, and a decent actor.
But I keep it in check, doing it mostly because humans tolerate badly total honesty, or sometime because I'm weak. Otherwise I avoid it, not for moral reason, be because somehow, I find it strongly unsatisfying. It's not even a judgemental voice in my head stating that it's wrong. It just feels like writting with the left hand with a boxing glove: I can do it with training but it's just not the experience I wish for.
I met many people sharing the same experience, but I can't say everybody feels like this.
However, it seems a damn good reason to be honest, even when it doesn't pay.