I'll offer my condolences too.
I can relate to you on this, My cat Cody died of lukiemia just a month back. But I know my familly gave him the best life he could ask for. I just hope his brother Sunny doesn't share that fatal flaw in his genes too. The best I can do is not worry about it, and be happy with him now. With luck Sunny will live a happy full life.
I remember Cody as he was, and celebrate his life rather than mourn his death. I'm sure you have loads of great memories with Maggie, don't forget them.