Most of these are invisible in bathroom lighting and obvious in daylight, which is why they persist.
1. Foundation that does not match
The most visible error there is. Fix: test on your jaw and neck, not your hand, and check in natural light. Between two shades, take the lighter one.
2. Not blending down the jaw
A visible line where the base stops. Fix: take it past the jawline and check the edge in daylight before leaving.
3. Concealer too light
Two shades lighter under the eyes creates pale patches. Fix: one step lighter than your foundation, no more.
4. Too much powder
It looks matte in the mirror and cakey by afternoon, especially on dry skin. Fix: powder the T-zone only, and lightly.
5. Dark liner all the way round the eye
Shrinks the eye. Fix: nude on the lower waterline, and reserve dark liner for the upper lash line and outer corner.
6. Over-plucked or over-drawn brows
Both make the face look harder. Fix: remove from below only, keep the front of the brow lightest, and brush through after filling.
7. Skipping the crease
Colour on the lid alone looks flat. Fix: one mid-tone shade in the crease adds depth in ten seconds.
8. Strong eyes and strong lips together
Reads as costume rather than makeup. Fix: pick one to be the feature.
9. Matte lipstick on dry lips
Emphasises every flake. Fix: exfoliate and balm beforehand, or use a satin formula on dry days.
10. Old products
Mascara past three months clumps whatever you do, and cream products separate. Fix: replace mascara quarterly, and check anything that has changed smell or texture.
The two habits that prevent most of this
Check in daylight. Bathroom lighting hides precisely what everyone else will see. A window is the only reliable mirror.
Use less. Almost every item on this list is a version of too much product. Starting with less and building is slower for about a week and better forever after.
More on each step in the makeup section.