Well, from my personal experience ( I'm almost 40 ), as you get older you sort of lose interest / endurance.
I mean these days I get bored pretty easily.
Oddly enough, I probably spend more time reading about video games on forums and magazines ten actually playing them.
Like I said, either I'm hard to please ( it might be the pirate syndrome as well mind you ) or after a little more then an hour playing I get headache and too tired to go on.
But then I find gems like Dishonored or Batman AC and I get all excited about it and the experience is so deep that I actually really enjoy it and can play for 3 - 4 hours straight........Or sometime I plug in my Xarcade joystick and start playing old arcade games till I beat them...
I also noticed that if I'm not serious about gaming ( not playing much ) I get tired very easily, but if I dedicate myself to it every day, then I can play decently again..
So in the end two things matters: Find content that you enjoy, and don't give up easily, start by doing short gaming sessions, then rest a little and give it another try.
You'll get better eventually !
I wish you happy gaming for years to come, you must have plenty of time now so don't give up, if you enjoy it, don't let anybody's judgement bother you, they are probably the old ones while you stayed young at heart

!