The lighting in your bathroom or vanity is likely not going to be the same as the lighting wherever your final destination is. In order to confirm your makeup is as flawless as can be, take a quick look when you get into the car. There is nothing truer than sunlight to show you imperfections big or small.
You may notice some discrepancy in color between your face & neck. Be sure to bring your cosmetic bag with you to touch up in the car!