in chapter 1 of the outsiders pony boy stated that he doesn't use his head. What is an example of him not using his head?

An example is when Ponyboy thinks Darry doesn't like him but he's just "not using his head".

Ponyboy was walking alone after the movie, and he knew he could easily get jumped by a group of Socs. It wasn't a smart thing to do.

Dally berates Ponyboy and states Ponyboy doesn't use his head when he notices he is walking around in a sweatshirt because he could die of pneumonia. This shows that both Dally and Darry care for Ponyboy's well being, even though Ponyboy doesn't realize it.