Once we have begun to follow Jesus, our lives should change. We know it. The problem is that we often struggle with how to do it. Paul gives us some practical instruction on how to change. It begins with a change in mind and follows with changes in action.
The first thing that has to change is our mind. Salvation comes when we repent and turn to God (Acts 3:19). Repent means to "change your mind." This is difficult because we have been taught how to think throughout our lives. These instructions may have been intentional (such as at school), secondary (such as at home, observing our parents or friends), or they may have been subconscious (through the variety of inputs we deal with daily - tv, music, movies, marketing). It is difficult to make the switch and begin to see all of our lives the way that God sees them. Our old lives and their value systems are gone. Now we must leave them and begin to seek the new life with God. Our hearts have to be focused on Him.
Changing our hearts and minds will result in changing our actions. Paul compares this process to changing clothes. When you spend time in the summer working in the yard, you come inside dirty, sweaty, and "aromatic". You take a shower to get cleaned up and then put on new, clean clothes. It would be crazy to put your old, filthy clothes on. Paul says that we should view our lives the same way. We come to Jesus and He forgives us and cleans us up. Then, the Holy Spirit guides us in putting away the actions of our old lives (or taking off the old clothes) and empowers us to live in a new way (put on clean clothes - Jesus).
The problem is that many Christians teach that the only parts of the process are getting cleaned up and taking off the old clothes. They neglect putting on a new life like the one Jesus lived. Instead of just "stopping everything", you need to replace an old habit with a new one that God desires. Instead of being greedy, start giving to other). Instead of complaining and being bitter, talk about the things that you are thankful for and forgive those who hurt you.
One of the key aspects of changing from your old life to your new life is moving from being self-centered to being others-centered. The most helpful thing you can do to make this change is to get involved in a community of people who love Jesus and are committed to following Him. The church is like a gym for those training to be like Jesus. We help one another focus on the right things - things above, not things below. We can encourage one another when we get discouraged. We also find that we are given the opportunity to practice and develop these new habits. Being around others gives us the opportunity to forgive, give, help, and love. It also enables us to become the recipients of those very same things. We experience the love, help, and forgiveness of others.
Change is hard, but it is not impossible. God has given you the ability to change through the forgiveness of Jesus, the power of the Holy Spirit, and the help of the church.