Combining these three verses together shows the basics of what Paul is teaching in regards to our ministry. We help other believers with their heavy loads. Please note, verse 1 speaks about a "fallen believer." This may very well be the "heavy load" that some carry. When a Christian sins they feel it! They feel weighed down with guilt and failure. They need someone to come along side them and help "lift them up" by showing the love and forgiveness of Christ and how they can be restored to fellowship.
Of course, other believers face daunting situations that require the help of others. Paul spoke about that in Romans 15:30 when he said that the believers were entering into "his struggles" by praying for him. Many believers need help in ministry and encouragement to keep going and not give up.
Then verse 5 speaks of our responsibility to carry are own loads, that is, to fulfill our own responsibilities as members of the Body of Christ. There are many passages in the New Testament that stress the importance of believers doing what they've been called to do so the rest of the Body benefits. Just think of the "hand that went to sleep" and know how that hinders the rest of your body until the hand "wakes up!" Too many Christians are "falling asleep" and not doing their share of the work, thus leaving other Christians to work extra hard. This is the picture in too many local churches.
Verse 9 tells us to watch out for "spiritual fatigue." We tend to get tired of the daily walk because it's not always exciting and other people seem to be having all the fun. The devil loves to tempt Christians to feel "they've done enough" or "others are resting, so why can't I?" Paul reminds us that the daily walk with the Lord WILL BRING GOOD RESULTS! We will "reap" a harvest of blessing at the proper time.
When you're tempted to slack off in your fervency for Christ try to remind yourself that other believers are depending on you. Feed on God's Word daily. Keep up with your life of prayer. Fellowship with other believers, thus allowing them to be an encouragement to you and you to them. Don't give up! "You will reap if you do not lost heart!"