As I get into Spring and getting my miles back up (25 miles max) I sometimes jolt myself into getting out of my comfort zone. To date I had only done a tad over 10 miles and wanted to get to doing 20 miles (and then 25) fairly soon to handle my commute to work. To do this I merely rode 10 miles away from my house which made me ride 10 miles back. As it was a cold and windy day the first 10 miles was a bit more painful than my normal 10 miles. The second 10 miles (wind now at my back) certainly hurt but my mindset was "Well I have to get home so I might as well keep going.". At times I went slower and twice on a hill I stopped to recover but in the end I made it. My legs were wiped out the rest of the day but on Sunday I felt great.
What made this work was that by going out and making myself get back I didn't allow my mind to limit me. As I mentioned above at the 10 mile mark I was ready to stop.... but couldn't. On a normal day I would have stopped at 10.
Going forward as I get more used to the 20 miles I'm not going to ride out 20 and come back 20 to get to 40. However I will certainly increase my miles by forcing myself away from an easy out. My "out" on all this was if I had physically reached my limit I could have called my wife for a shameful pickup but I would have to have been bad off to do that.
So.... the point is that sometimes you can overcome some of your mental limitations by putting yourself into a situation that makes it harder to quit. It's not dangerous like swimming out into the ocean and hoping you can get back, it's more that you can manage your mental hurdles and keep going. Doing one more painful lap when you are going right by your house is sometimes difficult but getting back to your house in the first place is doable.