The feeling that you can't move comes from lactic acid. When your muscles run out of oxygen (and i learned about cellular respiration a number of years ago, so pardon me if i'm fuzzy), for that extra bit of energy they'll use a form of fermentation, the byproduct of which is lactic acid.
This is what makes your muscles burn. When you work out consistently, your blood flow to those muscles improves, and you don't get the burn. You're still helping yourself.
If you feel like you can't move and it's not the post-workout burn, then yes you're still helping yourself and you'll be much better off aerobically in the future.
Then again, I could be entirely wrong.