There are times that we are being obliged to finish a specific task from other people. Our minds is being pushed in a work pressure to achieve the deadline. Of course, we can't afford ending up as a carcass when we fail to accomplish a task after the deadline. We see, that we will do everything to win their trust. Because of it, we opted to tell them promising words just to cure their anxiety towards us. We don't want them to be compromised so we end up saying, "I will do it, I PROMISE!".
Do you know that swearing is like putting yourself on the edge? Failure to accomplish what you have agreed will turn your expectation from white to black. Instead of gaining their trust, you gained their doubts of accomplishment to you or even will hate you. You don't want that to happen so you are compelled to do what's in the agreement.
The good impression is this, avoid swearing and just do it. Do it with all your best even if you fail. Having a strong statement, "I WILL DO IT!" will boost your confidence to accomplish a task. But having a weak statement, "I PROMISE.", is like opening a situation, a chances to "comPROMISE".
"DON'T PROMISE. JUST DO IT!", for action is better than words.