Lifehack.org has an interesting article entitled "But I can't…"
How often each day do you tell yourself, or others, you can't do something? Is it true? How do you know you can't? What if you're limiting yourself without knowing it? What if you're lying to save face or avoid embarrassment?
This is one of things I hope to overcome with the use of positive affirmations. I don't expect to notice any large changes just yet, but I'm quietly confident that they will have a positive effect on my life. "I can't" is simply a negative affirmation, and one I intend to ditch for good.