I used to have problems doing even 20 pushups. This was a problem when I was a freshman in college, since I was in ROTC at the time. I needed to do something about it, or else I wouldn't be able to pass the physical fitness test. (I ended up getting kicked out of ROTC for not passing the test in my senior year, but that's a different story). So, every day of Christmas break my freshman year, I did 100 pushups. When I got back, I was able to do the 41 pushups required to pass that portion of the test.
I have occasionally gone through periods of doing more pushups. I did more when I was taking kung fu. I did more for a while when someone I was dating mentioned liking buff men. Like most things I do in life, none of it lasted very long. Still, I get the urge to do pushups every so often, and I hardly ever deny myself the pleasure. I really feel like doing some now, but I don't know if I dare to in the office. I think I might have to be content with some stretching for now. We'll see.