Uncertainty is a very difficult thing to experience, as most people know. But it is certainty that is at the heart of the Lord's Good News message. He leaves His People in no doubt about where they stand.
One example is:
"... this is the testimony that
God has given us eternal life,
and this life is in His Son.
He who has the Son has life;
he who does not have the Son of God does not have life," 1 John 5'11-12.
"... knowing this, that our old man (old nature) was crucified with Him, that the body of sin might be done away with, that we should no longer be slaves of sin," Romans 6'6.
"... whatever you do, do it heartily,
knowing that from the Lord
you will receive the reward of the inheritance;
for you serve the Lord Christ," Colossians 3'23-24.
Do not lean on your own understanding, praise the Lord for the wonderful assurance of the word of Christ.