... when I am old I will do tai chi.
A great misconception.
Tai Chi Chuan training is one of the hardest things I've ever endured. The teacher began teaching the 60 students in our class by having us hold in each of the 64 stances while he slowly walked around and checked each and every one of the students' posture and the location of their hands and feet. This was in July at 11am on Sunday morning in a sub-tropical zone. It took about 20 minutes for him to check every student.
The man was sadistic. I think he actually enjoyed watching us suffer.
Then we would change to the next position and the ritual would start all over again!
Needless to say, we didn't appreciate students that could never get it right.
Practice sessions were three hours and at the end of it my legs were like rubber and I had lost about three quarts of water.
By comparison, aikido practice was easy.
P.S. There are no "easy" martial arts.