Ephesians 2:8-9: For by grace are ye saved through faith; and that not of yourselves: it is the gift of God: 9 Not of works, lest any man should boast.
Good works we do before Jesus takes charge of our hearts might help other men and win their approval but those works are worthless to God. They are done with the wrong motivation. They are done to benefit others and ultimately to benefit self. They are actually evil works because they can convince us and those that see them that we have a right relationship with God when we do not. They are not obedience to Him, nor do they establish a relationship with Him. They do not please Him or bring glory to Him.
Hebrews 11:6a: But without faith it is impossible to please him: . . .
Good works we do after we come to faith in Christ are immeasurably and eternally valuable and will be rewarded. They are performed by individuals that God has recreated for the precise purpose of doing works chosen by Him that accomplish His will, that please Him and that bring glory to Him.
Ephesians 2:10 For we are his workmanship, created in Christ Jesus unto good works, which God hath before ordained that we should walk in them.
Matthew 5:16: Let your light so shine before men, that they may see your good works, and glorify your Father which is in heaven.