"So overall in three years you have done pretty well (+10, +10, -8) = +12 but you have lost money and are back to square one."

This would be because of poor bankroll management.

"One thing I have noticed is that when I get ahead about 12-15% on NFL and MLB, bad things happen."

Sorry but this is silly.

"You might say that if you get a big winning streak you are minimizing your profit."

You are. Lowering your unit size to protect profits is a waste assuming long as each bet has percevied +EV.

"I bet short price favs"

Very few of these are good bets.

"In my opinion any progressive betting method on sports is doomed to failure unless you have a great method of backing outsiders."

Progressions are a bad idea full stop. A progression decides the size of a bet based on past results and not the size of advantage, which means at some point the progression will call for a bet size that will be overbetting.

That's enough for today heh