Your lifestyle is how you live, and it reflects who you are. You might try to look cool by adopting a rock star lifestyle of partying every night and sleeping all day, but you'd probably get pretty tired.
A lifestyle can also reflect your attitude or your personal values. For example, you might have a very conservative lifestyle, which means you don't spend money on anything trivial or unnecessary, and you don't engage in silly activities. A glamorous lifestyle means you indulge in upscale, high-profile pursuits and live luxuriously. If you've got some bad habits, your doctor might encourage you to adopt a healthier lifestyle, and get more exercise and eat more carefully.