Val, I went through the same type of thing with my mom, she had bad arthritis all her life. I would lose patience with her sometimes when I felt like she could do more.

When she died I felt guilty about those thoughts and times I showed it. You can never get this time back even if its not leukemia he is not getting any younger and you will probably be like me and keep mulling it all over. Tell him you love him as much as you can.