Jesus taught the liberation that we receive when we forgive others, that our Father in heaven will forgive us (Mark 11:25), but then Jesus just as quickly said,
“But if you do not forgive, neither will your Father in heaven forgive your trespasses” (Mark 11:26).
Our forgiveness is conditioned upon our forgiving others, and as Jesus said clearly, if we do not forgive others, our Father in heaven will not forgive us.
Imagine getting to the Judgment and learning that you have unforgiven sin and Jesus casts you into the outer darkness, all because you refused to forgive someone. Will it have been worth it?