Forgiveness:-
God so loved the world (世人) and gave the world His one and only Son - Lord Jesus Christ, who died on the cross as the eternal atonement of the sin of the world. God had done this amazing work for us long ago, and we are forgiven if we believe in Jesus Christ as our savior, will not perish but to have eternal life.

Hence we have to forgive others too: even though might be up to 77 times -Matthew 18:21-22; also if we do not forgive others their sins, our Father in heaven will not forgive our sins too. Matthew 6:14-15.

Consequences of sin:-
There is sin that does not lead to death (1 John 5:17). I think bitterness 苦毒 and selfishness 自私 are more at the disadvantage of the person who have them; but these bad behavior might open door or make it easier for other more serious sin to take its chance to slip inside our heart, to root and grow. James 1:14-16. ie If the devil cannot cause a strong person to fall immediately, it may still cause he or she to go astray slowly, to doubt a bit, to wonder away, tempt a little bit, sin a little bit. But when all these 'little nice' sin fully grown up - it gives birth to death.

At one time, Moses simply struck the rock for water as usual instead of to speak at the rock as commanded by the LORD. This seems like a very 'small matter', yet the consequence was serious. refer Number 20:8-12.

David simply walked on the root of a building ('too bold' even during war time) but this had let him see a beautiful lady... finally he committed adultery. David repented on this sin, yet he losses his child and got to suffer many other bad consequences...

Heavenly rewards
Those who hold on to the faith in the LORD, who run the proper race (1 Corinthians 9:24-27), who fight the good fight until finish/the end (2 Timothy 4:7) will definitely get their reward. And the reward is with our Lord. Revelation 22:11.
I think different people might have different reward. Your reward might not be relevant to me and vise versa. There is also general reward - long lasting, abundant and successful life.

For me, be able to sow more and reap more is a good reward because I used to fracture my hand, sick and cannot work, or to work hard but cannot get good result.