When the only walking you do is from your car to your desk and around your office, you might be able to get away with wearing shoes that don't fit quite properly. However, when you embark on a trip to explore a new city, you'll be walking miles each day. Ill-fitted footwear is bound to cause problems. If you're lucky, your poorly fitted shoes will just leave you with blisters. If you're not so lucky, you might end up with heel pain and sore tendons that linger for weeks.