You are what you do, not what you say you’ll do. -C.G. Jung

The quote suggests that you are defined by your actions and not by your words or intentions. People are going to remember what you did and not what you said or intended.

How can I apply it in my life?

Bring your focus on your actions, not what you want, not what you expect from others but what you are doing. Be aware of them in present. Once you are aware of your actions you will get better understanding of what is happening in your life.

Maintain a journal of your actions on daily or weekly basis and whenever something significant happens in your life (good or bad), refer this journal. See how you landed on that outcome.

Doing above activity will give you more clarity in your thinking. It will give you ability to make positive results consistent and negative ones obsolete.