Negative tú commands

Direct negative tú commands are formed by changing the -as ending of the tú form in the present tense to -es and the -es ending of the tú form to -as.
for the verb fumar: fumas-->fumes
for the verb correr: corres-->corras

Let's look at some examples of proper use:

¡No fumes! - Don't smoke!
¡No corras! - Don't run!
¡No duermas! - Don't sleep!
¡No comas! - Don't eat!
¡No vuelvas! - Don't come back!
¡No pienses! - Don't think!

No te pares.
Don't stop.