When people say everything is really fair in love and war, they mean they can do anything to win a war or love. Anything even something that is not fair is always acceptable in love and war.
Frankly speaking, I don't think that everything is really fair in love and war. If it is a war, you have to do a lot of things, but still there are rules and moral aspects. With power you can ignore that, but deep down you know that is not right.
You love someone, to get him/her or win his/her heart, you are ready to do anything. That is a good thing. It shows how much you love him or her. As a matter of fact, everything is not acceptable to get your boyfriend or girlfriend. There are moral aspects, you cannot deny that. You cannot be happy if you hurts someone only to get your boyfriend/girlfriend or your loved one. If you think clearly you can feel that there is something you cannot do, no matter how far it goes.
Doing the right thing is always right regardless of the situation you are in.
I think it that way.