People who has been through bad times try to forget that phase, but those around them try their level best to keep reminding them.
How and why can they do it? Simple, they give importance to the opinion of those persons. In life, when you have suffered you will see that if times are really bad, you suffer alone, and those who stay with you during that phase dont preach.
People who disappear with dark clouds are the one who preach most, or the ones who slam doors on your face.. So, why give any importance to their words?
In the beginning it will hurt, but with time and practice their words will be absolutely useless.