"If you avoid conflict, to keep the peace you start a war inside yourself"!!Watch
If you avoid conflict you're also more likely to be taken advantage of as you can't stand for your position as easily.
I believe this is called 'stonewalling'. Walking away mid arguement, saying things like whatever, im not talking about it, and generally ignoring the other person. However in a relationship even with friends or family, this causes resentment to poison the relationship. The other person is left feeling ignored and abandoned, like you dont care.
Avoiding conflict is sometimes not something that is done out of spitefullness, we generally dont see the big deal. But when its done on purpose, Its to punish the other person.
Its better to express how you feel. For example... When your mum is cleaning and moves the TV remote from next to you and puts it back whilst your watching something (they all do this) instead of saying... 'This really F***ks me off when you do that'... Its better to express how you feel... 'Mum i understand your cleaning, however i feel really frustrated when the remote is put back when im still watching TV'. The other person is less likely to react defensive.
Perhaps this other person feels you criticize instead of actually say what you want? - we all do this from time to time.
Hope this helps