I have found that the more I do Taiji, the more I am understanding the importance of stronger leg muscles. Since I have had a difficult time finding a partner to do the partner activities with, I have tried to find ways to build up these muscles in other ways.
Every morning I make a cup of coffee by first hand-grinding my coffee beans. So I decided that I would begin "sitting on the wall" while I ground up my beans. At first I could not last very long, but now I am able to stay sitting on the wall the entire time. So now I am also doing some squats while grinding my coffee, which is also helping.
I can tell a big difference now when I am doing a longer period of Taiji training, that my legs don't get worn out so quickly.