How To Write A Letter Of Regret . Consequently, we won’t get a chance to see you on. When you use ‘should have’, you mean that something did not happen, but you wish that it had happened. FREE 3+ Sample Resignation Letter with Regret in PDF MS Word from www.sampletemplates.com Help the recipient understand the reason for the rejection. Begin the body of the letter by thanking the person for their interest in the position. It was wrong of me to do this and i am truly sorry.