You think too much, but God Bless Ya!
I got a crazy thinker of a brain.
The bible puts it more classically: “run so as to win.”
Yeah... a guarantee to “win in the end” ought to warn us that kicks in the pants may be administered by the Lord to get us moving that way when we weren’t. The “doubt” applies to the small scale, not the ultimate scale. And it ought to, because we don’t know our own ignorance and unbelief until we encounter a situation that tests it. Another word for it is humility. “Lord I cannot do this.” To which He then answers “Yes with My power you can; here’s how.”