You might read a book called Rapid Chess Improvement by Michael de la Maza. I think he claimed something like being able to take a 1400 to an 1800 in 2 years. Or something like that. At any rate, it's worth a read (although most of the techniques are really tedious).
Before you buy de la Maza's book you should have a look at this review though:
http://dev.jeremysilman.com/shop/pc/Rapid-Chess-Improvement-p3511.htm
You have the ability, now its your turn to prove all those no-sayers wrong and take all your motivation to do it.