Healing isn't pretty.
"Healing" sounds like a nice word and maybe that's a problem. Healing doesn't happen painlessly but in an attempt to avoid any more pain, some people will avoid the healing process at all cost.
If you think of it physically, the healing of a cut or an accident, the event that caused the injury can happen in a split second but the healing can take a few days to a few years. A cut is first raw, then tender, and if someone bumps it even by accident it causes pain. It itches, is ugly, and sometimes leaves a scar. But then it's healed and the scar either becomes a reminder of the pain or a sign that you survived. You choose what to call it.
Healing happens naturally unless you prevent it by picking at it and reopening the wound. Doing so makes the healing take longer and creates more pain along the way.
Emotional and mental healing are no different. Some wounds take a short while but some may take years or almost an entire lifetime. You have to choose to acknowledge it and be conscious of when you're picking at it and you have to allow time to process.
Not every use of a knife will result in a cut and not every relationship will result in pain. Be aware and careful but don't avoid them altogether. They can be a helpful, wonderful part of life when implemented well, and you don't gain skill without practice. Pain can teach you compassion and resilience but only if you allow the healing to occur.