you are vs you're (informal speech)?

Question

In some common phrases like, "You are what you eat", "Your actions reflect who you are". Is there a reason (besides it sounds funny) to not use, "You're what you eat", "Your actions reflect who you're"?

Answer 1

Nothing grammatically incorrect with it! Just sounds funny!

Answer 2

There is no formal reason NOT to use the latter two examples, no ... but you're right, the former "sound funny," and that makes all the difference. It's a matter of prosody, and not grammar. Consider where the stresses / accents fall in each case:

You ARE what you EAT.

Your AC-tions re-FLECT who you ARE.

vs.

YOU'RE what you EAT.

Your AC-tions re-FLECT who YOU'RE.

The first two sound more natural; the latter two sound somewhat forced and awkward. The ear is often a good guide in such matters: if it sounds right, it probably is!