…is that we sit right next to our instrument. What sounds loud to us may only be a whisper at the back of a concert hall. What sound quiet might sound the same as our forte in the hall. Crescendos/diminuendos maybe sound huge to us but are nonexistent to the audience.
With such a small dynamic range to work with (compared to other instruments) guitarists have more work to do. We should try to push our limits, but that’s scary. When I want to get across to my students what loud is, I tell them to make the guitar sound gross loud. Not many can do that (get the strings to buzz, etc). The result is just a nice, loud sound.
Always exaggerate dynamics. Try to put yourself in the ears of the audience member at the back of the room — play to that person.