Attachment is essentially the brain's fear of losing control.
We all have things we can't let go of — a relationship that ended, a missed opportunity, words left unspoken. These things weigh on our hearts like stones, making it impossible to walk forward lightly.
Acceptance and Commitment Therapy (ACT) teaches us a counterintuitive truth: not all emotions need to be "solved." Some emotions just need to be accepted.

You don't need to "let go" — you just need to acknowledge its existence. Acknowledge "this hurts," then ask yourself: "Even with this pain, can I still choose how to live?"
The answer is usually yes.
Letting go isn't forgetting — it's moving forward with memories. You don't need to erase the past — you just need to let the past be the past, rather than letting it hijack your present.
The Zhuangzis said "飘风不终朝,骤雨不终日" — strong winds don't last all morning, heavy rain doesn't last all day. Even the most intense emotions will pass. You don't need to force yourself to "let go" — you just need to give time some time.