<human>: Could you distill the essence of the text into 1-3 sentences?

Hey, guys. I did a throwaway because this is strangely embarrassing for me, and I'd rather people I know didn't know about my petty worries.

So, until I was early teens, I was playing soccer, on running club, track, did hurdles, etc.  I loved running and being athletic.  Then, in high school, whenever I would jog just a bit or get my heart rate up a little, I would vomit.  I got blood tests galore and different meds, whatever.  I started smoking cigarettes, drinking a lot, eating whatever I wanted, and most of all, I NEVER exercised.  

Here I am now, at 21 years old, having quit smoking for three weeks now, 120 pounds (no muscle - my healthy weight is about 105 - I'm short) and about to go buy a pair of running shoes.

So here's my question; when I only jog one block and I'm out of breath, how do I not give up right then?  What are people going to think of me that saw me walk out of my house and I can't even run twenty yards?  What am I supposed to say to myself after side cramps, nausea, early fatigue, and simply put, failure?  

Sorry that this seems like such a silly post.  But I don't know.  I can't talk to anyone else about it.

P.S. It turned out the vomit thing was only GERD. It took them four years to figure that out.
<bot>: Used to be fit, now it's been years since I've done anything athletic, and I don't know how the hell I'm not going to give up since I know I'm going to fail.