I've heard it said that whether you think you CAN or think you can't, you're right. Your mind will act upon your thoughts and your actions will reflect your attitude.
So, it only makes sense to eliminate the "C" word from your vocabulary. In case you don't remember it, the "C" word is CAN'T.
How do you do this? Simply rephrase your thoughts to something more positive and embrace the possibilities.
"I can't get more customers." --> "I'm working on getting more customers."
"I can't get my head around this issue." --> "I haven't figured out how to solve this issue, but I'm working on it."
"I can't understand my teenager." --> "I need to improve my relationship with my teenager."
Okay - I'm not a therapist ; ) but you get the idea.
Remove the negativity and the absolutism of the "C" word and you'll be amazed what you CAN do.