I run occasionally to keep fit. Sometimes, I might not feel well and will not run in fear of endangering my life. I encounter instance of others collapsing while exercising when he/she feels unwell. It is better to avoid exercising to survive for another day. Apart from running, I do walk. I feel that walking is also a form of exercise. I will substitute running with walking if I happen to feel unwell for the day. I can control the intensity while walking.