These are a few things you could say as a closure goodbye message: "Despite the challenges we faced, I learned a lot from our relationship and I'm grateful for the memories we created." "I think it's important for both of us to move forward, and having this conversation has helped both of us do that." "I wish you all the best in your future endeavors and hope you find happiness and fulfillment." "Let's remember the good times we had, learn from the difficulties, and use these experiences to grow as individuals."