This combo of a military jacket and a grey crew-neck t-shirt is solid proof that a safe off-duty getup doesn't have to be boring. As for shoes, complete your ensemble with a pair of white canvas low top sneakers. If you often wonder how to dress age-appropriately, this getup is a good illustration.
If it's ease and practicality that you appreciate in a look, consider wearing a military jacket and a grey crew-neck t-shirt. Add a pair of beige canvas low top sneakers to the mix and ta-da: this ensemble is complete. This combination should erase any doubts you had about dressing casually as a 40-year-old man.