What is worse than sin? Pretending it does not exist. Proverbs 26:26 says, "Whose hatred is covered by deceit, his wickedness shall be shewed before the whole congregation. "
If you struggle with bitterness or hatred toward another person, the solution is not to pretend, but to replace. Ephesians 4 deals a lot with replacing the wrong of the sin nature with the right of Christ's nature (ie, "putting away lying, speak every man truth" or "let him that stole steal no more: but rather let him labour").
What must come first, before you can replace evil with good in your life - the thing that makes the real difference and ensures that you are not just pretending - is found in Ephesians 4:22-24. It says, "That ye put off concerning the former conversation the old man, which is corrupt according to the deceitful lusts; (23) And be renewed in the spirit of your mind; (24) And that ye put on the new man, which after God is created in righteousness and true holiness."
In order to have real, genuine change that is not simply pretending and covering the wickedness that is still there, you have to be changed spiritually. This comes from having a relationship with God, and daily, step-by-step fellowship with Him. In this way, the inward change shows itself in the outward actions.
Pretenders get exposed. Genuine Christians who walk with God, grow from their mistakes, and replace the evil of the sin nature with the character of Christ.
Do you know Christ as your Saviour? If not, trust Him and His death, burial, and resurrection to save your soul, and begin to walk with Him every moment of the day.
Romans 10:9-10, 13 "That if thou shalt confess with thy mouth the Lord Jesus, and shalt believe in thine heart that God hath raised him from the dead, thou shalt be saved. (10) For with the heart man believeth unto righteousness; and with the mouth confession is made unto salvation.... (13) For whosoever shall call upon the name of the Lord shall be saved."