Do not take wishful thinking to be belief. You cannot believe and doubt at the same time. Belief is certainty. You will not be anxious, worried or afraid if you believe. When you believe, you are sure.
If you truly believe you will do something, you will do it.
Many people think they have belief when they don’t. They only say it. They don’t believe.
The real sign of belief is success; the result you desire; not the proclamation of belief in words. If you say you believe you will do something but fail, it means you did not actually believe. You only claimed to believe. You only said the words.
People can only know you believe if you do the thing you say you believe you will do; and there is absolutely nothing you will not do if you believe you will do it.