You should learn when you should parry. Some good parrys are the parry out of hitstun and the Barker Bomb Bait.

Parry out of hitstun is when you both hit eachother at the same time and then go for a parry predicting his R1 out of the hitstun. When trying this you need to read there ping as with perfect ping you would parry as they hit while if they are lagging a bit you will need to parry much earlier or you might not even make it at all.

Barker Bomb Bait is when you throw a bomb(works with most thrown consumables) they roll past it and you prediction parry.

Depending on how good I think someone is, if they try these on me I will likely go for a backstab. So if you fight anyone you think might be decent probably not a good idea to try this unless they are consistantly doing it. Another thing is if you don't have a parry tool equipped then midway through the fight you suddenly swap to one, people will see this and predict the parry and get a free backstab a lot of the time.