If there is an enduring motto to Tai Chi (and any other martial art), it can be summed up in 3 little words....
"Just keep practising."
Whatever happens in your life, just keep practising. Even if it's just for 5 or 10 minutes, find something that you can do. When I first started, I didn't always have the time to dedicate to a whole session, so I used to do silk reeling in the photocopying room where I worked. I used to stand in Standing Pole or any of the Tai Chi postures while I was waiting for food to cook, or the kettle to boil.
When I'm not well, I usually concentrate on technique. I will stay seated and practise hand movements and shoulder alignment. From a seated position, I can also practise spinal alignment. I can also meditate, which is excellent for all martial arts. Mental practise is as important as physical. As long as I just keep practising, I know I'm going to be okay.
In an account about Lou Reed's last days before his death, he practised his form with just the hand movements, lying down in bed.
Practise is my default setting. If I'm upset, I practise. If I'm feeling good, I practise. When I'm bored, I practise. This compelling juxtaposition of posture and movement that we call Tai Chi keeps me endlessly fascinated and occupied.
I know that everything will be okay, as long as I just keep practising.