Disappointment is inevitable. But to become discouraged there's a choice I make. God would never discourage me. He would always point me to himself to trust him. Therefore my discouragement is from Satan. As you go through the emotions that we have hostility is not from God bitterness unforgiveness all of these are attacks from Satan.
In the latter case life rests upon a thousand presuppositions which the individual can never trace back to their origins and verify but which he must accept upon faith and belief.