In this passage, Paul speaks of being cast down. He was clearly discouraged with all that he had been through, and understandably so. It's interesting that he was comforted by something as simple as the arrival of a friend. I want to suggest however that Titus wasn't just any old friend, but the type of friend who had been through a lot with Paul and understood his problems. Titus was a friend who was there for Paul through thick and thin, and when the going got rough, Titus had Paul's back. It's no wonder that Paul was encouraged when his buddy arrived to comfort him during his time of need.
I've had a lot of friends throughout my life, but I can only think of three that I would consider to be in this catagory, and one is now with the Lord. These were guys I could call during the worse of times and they would be there for me. I could tell them my struggles, and they could tell me theirs. Often just by being around each other we would be mutually encouraged and rejuvinated. Friends such as these should never be taken for granted. If you have a friend like Titus, thank God for him or her. If not, pray that God would send you someone who would encourage and challenge you to live for Him, and comfort you when it gets hard. Also, purpose that you will be someone else's Titus.