Speak to yourself in a positive manner. How many times in a day do you say "I can't"? This could be at work, at the gym, while cooking dinner... I mean the list goes on ... and on... and on... It's such a simple thing to say, and we do it so easily. I remember once my yoga instructor told me instead of saying "I can't" - try saying, "thank you for coming this far and I look forward to going further."
I remember being in a shoulder stand thinking there is no way I can take my legs back and touch the floor. But instead, I tried the exercise she mentioned. I will kid you not, within weeks I was able to touch the floor. And this was just with yoga. I decided to apply this to every aspect of my life from then on. I changed my "I cants" to "one day I will." Without limiting myself verbally I was allowing myself to take the path that would only bring me closer to my dreams. I also wasn't setting dates - which I truly believe have a negative impact - I never told myself that I would be able to do this yoga move by this date, but instead told myself that one day I would get there I just don't know when and that is ok. So why not give it a chance?