|I hear people say "I can't" quite often. My kids use to say it all the time. You're basically hypnotizing yourself, telling your subconscious what it can't do. I'm sure I've said it also. These two words can do more than anything else to prevent you from learning something new like Microsoft Excel for example.|
This is also called a consistency bias. If you state something, you must be consistent with it, otherwise you go into a state of cognitive dissonance. Stating this "I can't" in public makes them even stronger.
Along with "I can't" you'll often hear people say "I'm not good at..." In the words of Henry Ford, "If you think you can, you're right. If you think you can't you're right." He also said, "If I'd ask people what they wanted they'd say 'Faster horses'". (This is not relevant, just one of my favorite quotes)
I would tell my kids, "Don't say I can't!, say I can't yet!"
I also hear people say, "I'm not technical", "I'm not good with computers", "Only kids can do it." Each of these statements may be true, but they're only a temporary state. Everyone that learned was once in this state.
"You can't teach an old dog a new trick." This may be true for dogs but not for people.