There is a huge difference between masturbating when your partner is not willing or available and rather masturbating than having sex even when your partner is willing. If your partner rather plays with himself/herself more than with you, that's not usually a very good sign...
Thought I have admit that I do watch porn mostly because I'm a selfish bastard who enjoys spending some time time-to-time just with myself. Porn is just I, me, myself and my dick. There is no need to worry about anything or having women giving you different kind of pressures or being dumb enough to actually expect that all the men actually have their dicks up 24/7 ready to have sex whenever woman wants (which is mostly a myth based on men just joking a lot more with each other than what they actually have sex in reality). When I watch porn, I can just lean back, relax and enjoy the show. I can watch anything I please, fast-forward past boring parts, replay, skip or change to another prettier woman during middle of the scene to keep constant sexual stimulation going. I can finish the job off quickly or fab all day long if thats what I'd like. There is no need to stress about anything, there is no need for any kind of communication, just fantasizing and enjoy... that's so called happy-me-time. Having real sex then again requires 2 people and correct moods and that's usually when things start to get easily more complicated...