Why does that soft charcoal always break so fast?

. . . Because you push too hard, or the pen has dropped before, it is easy to break.

Are you sure you mean charcoal? Instead of a stick or something? Like a pencil?

If it looks like a pencil, use a knife to shorten the refill and sharpen it slowly. Don't cut it too long I'd rather cut it a few times.

Grasp the strength of a good hand when using it. Not too heavy. The pen tip and the paper generally form an angle of 45.

If it's charcoal ... you don't have to cut it. ...