When John Proctor has finally abandoned his defense of his past wrong-doings and has no attachment to his farm anymore because he is in jail, all he has left is that which is in himself. He has no money to contribute, he cannot use his skills. These are the easy things for us to contribute because their cost is not our souls. When Proctor asks his wife who he has harmed greatly, what he should do, he releases absolute control of his soul to her discretion. This is true commitment.
I'm not suggesting that an individual should have such a wreckless abandon for their community, but sharing our souls would be a nice gesture. It's easy to bring in expired canned goods for a food drive for the needy, or throw a few quarters in the bucket for the Salvation Army standing outside a store during the holidays. But to write letters back and forth with an elderly woman that contain sincere encouragements or to play games with kids who need after school care on your street just out of the goodness of your heart, not because you want money, these are giving of your soul.
John was ready to make true sacrifice. For any society to work, it needs members that are devoted to its causes and purposes. Many people in America today have disagreed with the government for sometime. They are uniting in small groups at the local community level and are willing to risk and sacrifice people seeing them at a rally that demonstrates their position is against the norm, or at least against the currently elected majority. John was ready to sacrifice for something he believed was morally right while he was in a minority. He wanted Elizabeth to give him direction because it's harder to muster up the courage when you are in a minority.