Just think about how you might feel if someone never gave you a break for some of the mistakes you’ve made? Life would be pretty difficult if you continued to be judged for the way you were in the past, even if you were making an effort to change for the better.
Keep that in mind the next time you get upset with someone. Consider that one day you might (accidentally or maybe even intentionally) do something similar, and imagine how you would like to be treated. Would you want to be ‘written off’ and judged for that action for the rest of your life? Of course not! So why do that to another person?