If you know you will get a lot of No's in this modeling pursuit then you will be able to over come the pitfalls, the days you aren't booking that job you really wanted, and how to get over a casting you didn't get and move on and chase more!
If you are modeling just to feel good about yourself, or feel pretty or liked, then I think you shouldn't model at all. Modeling to me is about chances, it is about staying positive, driven and hungry. And it is a pursuit that doesn't happen easily. It can take mailing 50 compcard until you hear back from one casting director or modeling agency. It can take 10 castings before you even get one call back.
So it is best to expect the NO's, and know this business of modeling involves ALOT of them. It is a competitive business but also alot is possible. Staying ambitious is key!