I am trying very hard to become a lover and carer of plants, and I'm doing much better than before, however I have not been able to bring my Christmas Cactus back....his little leaves are yellow and he has not grown in size for two years. Any suggestions? I hate to throw him away? He is outside and until today, he was in the Texas summer sun. Now I have moved him to the shade (all great gardeners are cringing). I want to be better and see this cactus thrive! He was inside but he wasn't doing too good indoors either.