“The one who calls you is faithful, and he will do it” (1 Thessalonians 5:24).
If you are living a purpose-driven life for Christ, there will be times when others do not understand the work you do for Him. They will judge your motives or question if you are really doing what God has called you to do. Don't hinder His work by feeling you have to justify your calling. If you try, you will fail, and it will bring spiritual frustration. It is not your place to explain. It is His place. Any explanation or justification must come from Him. Just do your work in His name, and the result will be your reward.
Keep your heart humble and pliable in His hands. Realize those who question your calling have their own hurts, pains, and needs. Place yourself in their shoes to understand the reasons that they question your motives. Pray for these reasons to be resolved in their lives. Sometimes it is jealousy because they feel inadequate in their own Christian lives. Sometimes it is jealously that God has not brought forth their own promise. Sometimes it comes from spiritual legalism. Whatever the problem, don't try to take care of it within your own strength. In any difficulty with another put yourself in his place and pray that his problem with you will be resolved. Be humble enough to know that you are not perfect, and sometimes there must be a change in your own perspective.
The power to realize the needs of others can only come through a yielded and loving life. It can only come by continual contact with God in prayer and purpose. You can't do your work without deep spiritual contact with Him, and you can't put yourself in another person's place without His love alive and well in you.
When you understand your calling and live it–when you know you don't have to justify it‒ when you put yourself in someone's place to understand why he might judge you‒when you pray for God to work mightily in that person's life‒when you pray for God to keep you humble‒when you honestly assess what you do in His name‒when your will is totally yielded to God‒then you are walking in His spirit. You are an instrument to be used at God's will. You will know the fulfillment of being in His will, and the flowing freedom of His spirit.
Your purpose is to live a life which reveals His power working through a surrendered and yielded life. His purpose is to do the work.