What does Darry mean when he says "you don't just stop living because you lose somebody"?

In Chapter 12, Ponyboy and Darry get into a fight about completing homework. Ponyboy tells Darry that he doesn't see what the big deal is about schoolwork and says that he's going to get a job like Sodapop when he drops out. Darry corrects Ponyboy and tells him that he needs to start giving more effort because he has the skills it takes to earn a college scholarship. He then says,

"You're living in a...

In Chapter 12, Ponyboy and Darry get into a fight about completing homework. Ponyboy tells Darry that he doesn't see what the big deal is about schoolwork and says that he's going to get a job like Sodapop when he drops out. Darry corrects Ponyboy and tells him that he needs to start giving more effort because he has the skills it takes to earn a college scholarship. He then says,

"You're living in a vacuum, Pony, and you're going to have to cut it out. Johnny and Dallas were our buddies, too, but you don't just stop living because you lose someone" (Hinton 148).

Darry is trying to encourage Ponyboy to start living his life again. He feels that Ponyboy has lost focus after witnessing the tragic deaths of his two friends. Darry understands the importance of setting goals and staying focused during tough times. If Ponyboy continues to pity himself and not give effort in the classroom, he will waste his talents. Darry is trying to encourage Ponyboy to snap out of his depression and begin living with a purpose again.