But he said to me, "My grace is sufficient for you, for my power is made perfect in weakness." Therefore I will boast all the more gladly about my weaknesses, so that Christ's power may rest on me.
The Bible is by no means telling you to rejoice in sin. It also isn't telling you to use this verse as an excuse to sin.
Finally, this verse is not talking about boasting in your flesh, in what you have, it is talking about boasting in the knowledge that you are nothing and can do nothing without Jesus Christ's power.
Total reliance, 100%.
This is what the LORD says: "Cursed is the one who trusts in man, who depends on flesh for his strength and whose heart turns away from the LORD.This Bible verse, God's own words through His prophet, is not just talking about others, it's talking about you too.
It IS NOT saying that you should be cowardly and not be confident in who God made you to be, but be confident in who God made you to be while you are in Him. (We're sitted in Heavenly places with/in Christ Jesus)
Total Reliance on God is this: Admitting from and in your heart that you are weak, you can do nothing without God's help and God's help is enough.
Forget man. Forget me. Only God will not disappoint you. Only God is guaranteed 100% to never let you down.