Lower EQ can be caused by a lot of different things, not just the mental state. If you are still pulling 8/9s (I assume that you are using a 1-10 scale and the 11 is a nod to Spinal Tap), then sex should not be a problem, just pride, eh?
For a while, I went through a period of 2-4 grade erections - like trying to fuck with a wet noodle. It sucked. But I got fixed up (surgery - long story) and now I am back to 8/9s with occasional 10s.
So, think about all the things that may have caused the change: diet, smoking?, injury, lack of exercise, bike/horse riding, medication(s), life change (death in family, new job, big move)… If there is no compelling physical/emotional reason, then yeah, you may just have to force yourself to like 8/9s and be happy with the occasional 10. You are, sad to say, not a teenager anymore. That does not mean that you perforce lose your superboner ability, but they do tend to happen a little less frequently and not at the drop of a hat. I found that by not worrying about how hard my dick is allows me to relax and focus on the pleasure that it is providing me, and I usually end up getting harder as a consequence.
Good luck!