Prayer has nothing to do with religion, it is not a ritual, nor is it limited to specific occasions. The most important thing is from daily intentions. When you pray for your sister with the idea that she always wants to get better soon, it is equivalent to giving him some confidence. For yourself, anything that you can concentrate on will give you strength without affecting your health.
Health means that a normal person has no disease, strong activity ability and labor ability, positive and optimistic mental health, can adapt to society well, and has correct morality and values.