Don't laugh! It sounds so simple but it is such a common mistake.
Disclaimer: This is not me!
Today I decided to use my Benefit Dallas bronzer to contour my cheekbones before heading out to run some errands. After I left the house I got a few weird looks and little chuckles, I didn't think much of it because I hadn't straightened my hair so assumed that I was walking with a frizz ball on top of my head. (OMG, it actually hurts to write this!) I finally stopped in front of a mirror to sort out my hair and was gobsmacked to see 2 very clear brown lines on both sides of my face - I HADN'T BLENDED PROPERLY! The dark lighting in my room had led me to believe that I had blended the bronzer in properly but in the clear light outside I could see how defined they were. DAMN.YOU.ROOM! This led to some furious rubbing of my cheeks which ended up VERY RED! Oh dear...
Anyway, enough of my sob stories! When applying make-up make sure that you are in natural light and always make sure that you have a quick look in your compact mirror once you've left the house. Dark lighting means that you will cake on the make-up because you can't see it!
Have you had a similar experience to mine?