Saul’s reign lasts forty-two years, but the entirety of it is summed up between chapters eleven through fifteen of 1 Samuel.
We also know it by its religious name: faithlessness.
Saul had every reason to trust God. In chapter ten of our reading, Samuel gives a timid Saul three signs that he is indeed the chosen person to lead Israel. Sometimes we can get off track with the reading because we don’t know what the business of “prophesying” was in that particular context. But it is unimportant. The important thing is that neither it nor any of the other signs could have been accomplished without divine intervention. God is in the appointment. Saul should trust the Lord.
And indeed, Saul’s heart is changed and in chapter eleven he leads valiantly. But it doesn’t last. Saul’s fear is seen in his hiding among the baggage. It is seen again in chapter thirteen in his fear of the Philistimes. You see it again in his fear of his own people (chapter 16). Saul is changed, but the change doesn’t stick.
When God accepts us into His family, forgives us and indwells us by His Spirit, we are changed. It is, however, up to us (not entirely – but significantly) to maintain the change by trusting in God and acknowledging with our behavior that His way is right.