One of the worst days of my life

I had to take our little kitty Lucy (well she was about 5 years old) to be put to sleep today. I didn't think it would affect me as much as it is. A friend of ours found her in a drainage ditch when she was about 6 weeks old so we took her in. She never really got very big, she was a petite little thing. But anyways she has also had a mental problem lets say. She was not a social cat and we only saw her occasionally. She camped out under my bed most of the time. We still loved her. The last year she has taken it upon herself to use anything in the house to use as her litter box. We have taken her to the vet to make sure that she didn't have a medical problem and she didn't. So we put up with it long enough. Something had to be done. I just need to vent and thought this would be the best place. My girls are not taking it any better than I am. I told my dh that the next time a pet needs to be put to sleep he is taking it. It just hurt so much.