That's part of life. It's your job NOT to accept it. Fuck me, not a day goes by where I don't feel like I'm fallin apart at the seams at some point in the day if not all day. But I fight it. I fight being in my late 30's, I fight having gained so much weight these last few years, I fight the "old" feeling of having a 15yr old daughter, an old car, not enought money, and slowly sagging balls.
Some days I win, some days I don't.
Doc's quote hits the nead on the nail.
"You don't stop doing the things you love because you get old -- you get old, because you stop doing the things you love."
Revive your passions. You tend to get lost along the way, lose sight, can't see the forest through the trees, etc, etc. Sometimes, it's not the things you do that get boring. It's you that needs to change the way you do those things. It's you that's become boring.