WHY SHOULD I FORGIVE?

Grudges. What are they good for? Grudges if nurtured and cultivated will get too heavy to carry and will break you under the pressure eventually until you explode with wrath. The bible tells us not to let the sun go down on our anger. If we harbor ill feelings against another it will just become a cancer that eats away at our happiness and peace.
Ephesians 4:26 Be ye angry, and sin not: let not the sun go down upon your wrath: 27 Neither give place to the devil.
     The thing we see here from scripture is that holding on to our anger against another will give place to the devil. If we hold grudges for too long we are giving the devil a foothold in our heart to tempt us to work all kinds of evil. The flesh hungers to see vengeance against our perceived enemies and plays right into the hand of the devil. So who is the REAL enemy? It is our flesh and the devil that are the real criminals. 
Galatians 5:19 Now the works of the flesh are manifest, which are these; Adultery, fornication, uncleanness, lasciviousness, 20 Idolatry, witchcraft, hatred, variance, emulations, wrath, strife, seditions, heresies, 21 Envyings, murders, drunkenness, revellings, and such like: of the which I tell you before, as I have also told you in time past, that they which do such things shall not inherit the kingdom of God.
     Clearly scripture reveals these truths that are the principles that will destroy us if allowed to become full grown. But we should not wrestle against other people. Especially children of God. But we should show them the love of God (agape love) which is unconditional.
1 Corinthians 13:4 Charity suffereth long, and is kind; charity envieth not; charity vaunteth not itself, is not puffed up, 5 Doth not behave itself unseemly, seeketh not her own, is not easily provoked, thinketh no evil; 6 Rejoiceth not in iniquity, but rejoiceth in the truth; 7 Beareth all things, believeth all things, hopeth all things, endureth all things.
      What we can see from this passage is that love never fails or in other words it never ends because this is the God kind of love. This love is unconditional. It is not based on performance. It is much like the love a parent has for his child. A parent always wants to think the best about his child sometimes even in the face of overwhelming evidence. But the parent goes on undaunted in their support for their child because of unconditional love. Parents to be most of the time have this kind of love for the child they have not met as of yet. This love begins at conception, the very thought of having the child. This kind of love NEVER ends and is not dependent on any works because the child has not even been born yet. 
Ephesians 6:12 For we wrestle not against flesh and blood, but against principalities, against powers, against the rulers of the darkness of this world, against spiritual wickedness in high places.
     The only way we can hope to deal with someone who has wronged us is by utilizing this type of love. We must realize that we are dealing with principles but the principles of the flesh are influenced by wrong thinking and the temptation of the devil. If we follow God's rule of what love is we will forgive even if we feel the other does not deserve it giving up the judgement to the TRUE judge which is God. 
Romans 12:1 I beseech you therefore, brethren, by the mercies of God, that ye present your bodies a living sacrifice, holy, acceptable unto God, which is your reasonable service. 2 And be not conformed to this world: but be ye transformed by the renewing of your mind, that ye may prove what is that good, and acceptable, and perfect, will of God.
     A good tactic that I like to use is to see my anger or hatred against another as a living sacrifice that I give to God. I must be willing to offer this sacrifice to God so that I can have a clear conscience before Him and enter boldly into the throne of Grace. 
     Just as God will answer the prayer of faith for things like healing, finances, courage, salvation, etc. He will also answer the prayer for deliverance from anger. So in order to sacrifice the lust for vengeance against another we can go to God and ask Him to take away our bitterness against another and nail it to the cross of Jesus and let it die there.
     In conclusion, don't let your grudges grow so big that they crush you.