I decided that next day that I could only lose that unwanted excess skin under my arms if I did 100 push-ups and 100 triceps dips every day. Up until that point, I could do something like 30 push-ups. I was that lazy kid once-upon-a-time who did .5 of them in gym class before I got too tired to do any more, but that changed as I got older. I worked at it, and soon I could do 5 on my toes. Then, I made it up to 10. Then 20. When I did P90X last year, I could do up to 30 push-ups without stopping. That was a gigantic accomplishment for me.
The day after I decided to do my 100 push-ups, I did 100 of them. I did 20 push-ups, and then I flipped over and did 20 triceps dips. Then, I flipped back over and did 20 push-ups. I got tired quickly, but I took breaks and did them. I stuck with my goal, and I did this every day for a few weeks. Soon enough, I could divide my push-ups into 4 sets of 25. I did this all on my toes. I never dropped down to my knees.
When I put on my dress for the final time before my wedding (I had three dress fittings), that unwanted skin was gone. It vanished. My arms looked more toned to me than they ever did before, and I was so proud of my hard work.
I don't consider myself to be an athletic person, but I am a good example of the fact that a little work goes a long way. Even if you can barely do a full push-up right now, I am living proof that you can do 100. Just take baby steps, and you will do it!