The words you choose can determine your success. If a person can’t do it, they are missing the skills to perform. If a person won’t do it, they may be missing the will, drive or understanding to why they should do what is expected. Substituting “I won’t” for “I can’t” lets you off the hook but you should take responsibility for your actions rather than making excuses and use those words appropriately.
The words we use have a far greater effect on our mentality than their obvious grammatical application. The word can’t literally alter our perspective and beliefs in an instant. It presupposes that we don’t have the ability or the resources to get the result, which in most cases, is not true at all. Eventually we believe what we repeatedly tell ourselves — whether it’s factual or not. Before long, our creativity gradually disappears and we adjust / lower our expectations — only to set the stage for further disappointment in the future. There are certain appropriate occasions to use the word “can’t,” but many times, we use it to hide a deeper concern or fear. Rarely is it used to indicate that something is actually impossible. It’s often just a crutch we use to suppress the real reasons we choose not to take further action.

We choose to use the word “can’t” when the process involves fear, inconvenience, or sacrifices that we are unwilling to endure.

It’s often the very things we’re putting off that will take us closer to where we really want to be.