Diamond Push-up

You flare the elbows out to the sides, which defeats the narrow-grip purpose and stresses the wrists and shoulders.

You place the diamond too high, under the face instead of under the chest, shortening the range and straining the shoulders.

You let the hips drop as the triceps fatigue, using body sag to sneak the chest to the hands.

Keep the elbows brushing your ribs the whole way down and up so the triceps do the work.

Push the floor away hard at the top and hold the lockout for a beat to finish the triceps.

If full reps break down, drop to your knees and keep the elbow path strict rather than flaring to survive.