I believe the greatest fear that a person can face is the thought of leaving their loved ones.
Explanation:
When a person faces certain death they always have one emotion and that emotion is fear. The person feels fear of leaving their loved ones, the fear of not being able to achieve what they wanted in life, and the uncertainty of not living. Its a scary thought to be thinking about but life happens and theres always an end to it.
You should not exercise in the cold because it's really bad for your bones, and you will get dehydrated and pass out if you're exercising in extreme heat.