Speaking as someone who works in sales- you say right out that you don't handle rejection well, so you rarely 'put yourself out there'. Believe me, I understand! My entire JOB is calling people and believe me, I get rejected a LOT in this economy!
It can be frustrating, depressing, etc- especially if someone has encouraged me on the phone, asked for more info, made follow-ups and indicated that they were interested in advertising with my publication ( I sell advertising) -so I invest a lot of time and effort into them- and then NOTHING!
But- here is the key thing, that I can pass on to you as a salesperson:
Don't Take It Personally!!
You may have had all the qualifications. You may have had a great interview.But if they still said no- MOVE ON. Seriously, just do not dwell on. It was not you personally- just that the position, for whatever reason, was not the right fit.
Tell yourself that even though you may NEED the job- if they honestly didn't think it would be the best fit and had hired you anyway, you might have been miserable there!
At any rate- next time, before you go on an interview, have 5 more places lined up to call as soon as you get out. No matter how well it goes, call those 5 other places. IT IS NOT PERSONAL- it does not reflect on you being a good person, a good mom, a good anything. It's just the way it is- don't allow it to get you down on yourself!!!