Having good credit is easier said than done. Think being responsible and paying your bills on time is enough to keep your credit score high? Think again. When applying for a mortgage or any large loan, your credit score can mean the difference between being approved and denied. Even if you are approved, your credit score determines the interest rate of your loan. If you don't have good credit, you could end up paying thousands in interest alone. You may think you’re on the right track, but these seven practices can negatively affect your financing and lower your credit score.