Situations where you have to stand up for yourself, will always arise. Whether it is someone who stepped on your freshly polished shoes or a colleague who gets credit for your hard work, you need to react. Of course, not every situation warrants a response but there are those incidents where you must speak up for yourself because no one else will.
This in no way involves conflict, strife or violence. Quite the contrary. It is about stating the facts of what happened calmly. If you feel anger or resentment at that moment, it is best to hold yourself back until you have cooled down.