You've probably heard the saying before that, "men are more visual." While I think the reality is a little more nuanced than that, this phrase often becomes a self-fulfilling prophecy for many men when it comes to experiencing pleasure.
Many men feel that their arousal is heavily connected to and dependent upon how they perceive their partner's experience to be. Men derive a lot of their own pleasure from their partner's expression of pleasure. The more excited, wet, vocal, etcetera that their partner gets, the more excited he gets.
Men care that their partner looks like they're enjoying themselves during sex. Contrary to popular belief, many men wouldn't have sex with an unmoved and physically non-responsive partner.
However, his reliance on pleasure being derived solely from what his partner looks like and whether he perceives that they're having a good time can be detrimental.
Firstly, he shoots himself in the foot regarding his own pleasure because he is experiencing pleasure vicariously through his partner. He is experiencing pleasure indirectly, thus it will be less than would he could potentially be able to feel.
Secondly, he puts pressure on his partner to look a certain way and to also express their pleasure so that he can experience pleasure. This is one reason why so many women feel the need to fake their orgasms.
So, if this sounds like something you've been doing, it might be time to change. Chiropractor and Sexological Bodyworker Betty Martin suggests that, instead of taking the indirect route to pleasure, you could take the direct route. This means focussing on the pleasurable sensations that you actually physically feel from touching or being touched by something or someone.
You can practice this when masturbating. If you're watching porn, rather than focussing solely on the person(s) in the photo/video on the screen, experiencing pleasure vicariously through them, try shifting your attention to your hands and your cock. Notice what pleasurable feelings arise when you touch yourself in a certain way. Allow pleasure to take a direct route.