Capacity is a state of mind. How much we can do depends on how much we think we can do. According to the self-fulfilling prophecy: you are what you think you are.
If you believe that you can achieve your dreams, you can and you will. If you believe that you are lazy, too busy, a failure, and many other horrible things that we say to ourselves sometimes, those will come true, too.
What kind of thoughts are you thinking today? Change your thoughts, change your life!