Your life is a marathon, not a sprint: and you have plenty of ground left to cover. So do things today that help conserve your energy, not use it all up. Physical activity is fine, but just don't go overboard or try to show off. There's a risk of injury or embarrassment (neither of which is very pleasant to consider). Keep working away at a person you're trying to deal with. If they're trying to get the better of you, your perseverance won't let them win.