If you declare with your mouth, “Jesus is Lord,” and believe in your heart that God raised him from the dead, you will be saved. For it is with your heart that you believe and are justified, and it is with your mouth that you profess your faith and are saved. Romans 10:9-10 (New International Version)
Belief should be the decision that drives all of your actions forward.
Only if one believes in something can one act purposefully. If you believe it, you will act upon it. If you don’t believe in something, you will not do what you are saying you believe.
What are your actions saying about your belief?