“Wherefore the rather, brethren, give diligence to make your calling and election sure: for if ye do these things, ye shall never fall:”
2 Peter 1:10

He begins:
“And beside this, giving all diligence, add to your faith virtue; and to virtue knowledge;” 2 Peter 1:5
Give all diligence! You can’t afford to be a lazy or unserious believer, God “…he is a rewarder of them that diligently seek him.” Hebrews 11:6
“Seest thou a man diligent in his business? he shall stand before kings; he shall not stand before mean men.” Proverbs 22:29
Diligence means giving attention to a thing, and exuding serious promptness concerning a matter. He says to ensure you never fall, you must diligently make your calling and election sure, and he begins by telling you to add virtue to your faith. Faith was ministered to you when you heard the gospel, and with that faith you accepted the gospel and became born again:
“So then faith cometh by hearing, and hearing by the word of God.” Romans 10:17
Now that you are born again, you don’t just sleep off or continue acting like an unbeliever, he says add something to your life- you should ensure you increase in your expressions of virtue- moral excellence, because you are born again, there should be some excellence about your life, a consciousness in your expressions of faith and a moral goodness about you- he says be diligent in abounding in such expressions.