How do I go about firing someone that works for me in a nice manner?

I have a guy that mows my grass and has for the past 3 years. Last year, he started slacking, mowing only every couple of weeks or even every 3 weeks. He told me he was going through a divorce and was having a bad time of it, so I let it slide. This mowing season started out pretty good, but now, I haven’t seen him for over 2 weeks. I called him, he had another sad story of losing 12 customers, etc. and would be over the next day. 5 days later, I still haven’t seen him. I am done with him, so how do I tell him?