He sinned against the Lord because he feared the people and would not stand for what was right before God. Saul would not stand for what was right because he was afraid of the people. The most important thing you will ever do in life is to obey God. The Bible has instances of both them who obeyed and those who disobeyed. It is the obedient that receives God's richest blessings.
Disobedience brings trouble while obedience brings blessing.
I love to see the Bible instances of the obedient. 1- Angels obey the Lord. Jesus obeyed the Father. 3- Saints are elected unto obedience. Noah obeyed the Lord.