Attachment is another name of disappointment and pain. Accept what comes and allow it to leave when it is time. Attachment is your biggest strength and your biggest weakness as it becomes difficult to live when you lose something you are attached to. Letting go is never easy weather it is a relationship, a friend, your ego, or even a job it can be hard to let go of attachments because it feels like you are letting go of some part of yourself. Renew, release, let go. Yesterday's gone. There is nothing you can do to bring it back. So you can't "should've" done something. You can only Do something. Renew yourself. Release that attachment. Today is a new day.