On-trend yet comfy, this look is assembled from a sweatshirt and navy jeans. Athletic shoes are a guaranteed way to give a dose of stylish nonchalance to your outfit. During winter, when comfort is key, it can be easy to surrender to a less-than-stylish outfit. This outfit, however, is a bright example that you can actually stay warm and remain stylish during winter. Now that's how you keep it casual in the style department in your mid-20s.