To be free of guilt and negative self attacks, we must pay our debts. Not only the monetary ones, but the ones which caused harm to someone because of your actions.
When you do something or advise someone do something which causes them harm, you will naturally feel bad, if you have even a thread of conscience.
To be free emotionally, we must open our hearts and feel all things, love and pain, this is compassion.
But if we took responsibility for all our actions, and saw how much we inadvertently hurt other people in some way, it would be too painful.
To deal with this, we blind ourselves to the repercussions of our actions, but this simultaneously closes our heart.
If you want to live in peace, harm no one, and if you do, make up for your actions as quickly as possible. Pay your debts and leave no trace of harm in the wake of your life.
It may cost you a lot of your own money or possessions, even if you could find ways to justify that it is not entirely your doing, but if you set the wheels in motion down a rocky path, then you know what you did.
This is why our hearts are shut. We did not close our heart to feeling closer to other people, it is closed to avoid feeling close to our own self, the one who remembers all its harmful actions.
People often say that they closed their heart because they have been hurt by someone, and I agree, this is often true, but it is not the entire problem. We close our heart to protect ourself from what others may do to us, which is our projection based on what we have done to others.
There is a saying, an honest person trusts everyone and a thief trusts no one. In the same way, if your heart is closed, instead of blaming or remembering the heartbreaks you felt, just look at your own actions and what debts you still owe.
Make a list of anyone you may have hurt, send them a letter, call to chat, do something, and let your regret be expressed. Even better, do what you can to make up for their loss.
You will find that very quickly, your heart becomes lighter and more open.
Think about this, in Buddhism and many other religions, they do not say to not love, but they do say to not kill. There is no harm in loving, but there is harm in killing.
The victim is out and free of this life. The one who did the harm is stuck here burning in memories and regret. Killing is of course a drastic example, but the principle applies equally to any act of causing harm.