Why does Two-bit tell Ponyboy "Don't get tough. You're not like the rest if us and don't try to be..."?
Two-bit does not want Pony to be dragged into the life of violence.
Ponyboy is different, and the other boys in the gang know this. They do not look down on it, and in fact they appreciate it. Two-bit and Johnny both have the same sentiment. Johnny asked Pony to "stay gold." After Johnny’s death, Two-bit and the others may fear that Ponyboy might get dragged into the revenge cycle, getting into a rumble to fight the Socs and get himself killed in order to avenge Johnny’s death. Yet unlike the rest of them, Pony has intelligence and the ability to make a different kind of life for himself, as writing his story demonstrates.
This conversation comes to pass when Pony is confronted by a Soc who accosts him as “the guy that killed Bob Sheldon,” and threatens him. Pony decides he’s not afraid, and casually breaks a bottle to use as a weapon. They are surprised, and leave. Two-bit is watching, and when Pony continues to pick up the glass he tells him not to be tough like the others. Then he realizes why Pony is picking it up.
"You little sonofagun," he said in a relieved voice. I didn't know what he was talking about, so I just went on picking up the glass from the bottle end and put it in a trash can. I didn't want anyone to get a flat tire. (Ch. 12)
This exchange demonstrates that Pony is at peace with himself. While he was not afraid of the Socs and was able to defend himself, he also picks up the pieces of glass so no one will get a flat tire. He’s not “tough.” He is himself. He is no patsy. Pony has been through a lot, and he is still a sensitive soul. He has a chance to grow up and be more than a greaser. The Socs too will see him as someone other than a greaser, but they will see him as someone who can defend himself. Two-bit realizes that Pony will be all right.
Ponyboy is a nice guy and from the start he never wanted to kill anyone. Two bit doesn't want Ponyboy to turn into anyone and change into something he's not or get in a scuffle and get killed. He wants him to be himself.
Since in the beginning of the book Ponyboy would not harm anyone and he doesn't want him to change into them. Even worse he doesn't want Pony to change into Dally and get himself killed.
He doesn't want Pony Boy to life the life he has to live. It's a life full of gang fights and unsafe for Pony Boy just like when Pony Boy was told to stay golden. This was because they wanted to maintain Pony Boy's innocence. He knows Pony Boy can live a normal fun life and interact with others beside just the greasers and that he will be just fine. It's a great book!!!!