"I always feel that I have in some way failed our Lord." This is not an uncommon sentiment shared by many who strive to serve the Lord with all their heart.
If the day comes when you are satisfied with your service and don't feel you have failed in some way, that is the day your heart has dimmed in expression of His love you desire to express in service to another. This is a good thing. This is a good thing! Do not look upon that sense within you you express as being something negative or lacking. It is not.
Unlike Him, we do not know the mysterious work, the comings and goings of the Holy Spirit. We can not. (John 3:8) At best, we only see through a glass darkly. (I Corinthians 13:12) But we do know in our heart He has called and commissioned us into that mysterious service. (II Corinthians 5:18) As He spoke only that and all that the Father had spoken to Him to speak to others, when we have spoken in service all He put within our hearts to say, then our heart should not condemn us. (John 12:49) As He did only that and all that the Father had shown Him to do for others, when we have done in service all He put within our hearts to do, then our heart should not condemn us. That is the sum total of our calling and service as well. (John 16:13; John 15:15-16; John 17:16-20; Romans 10:13-15; John 3:8)
Paul was a man always striving to do his best for His Master. He longed for the perfection he knew lay within the power of the resurrection of our Lord. (Philippians 3) He desired to totally live within that power but he knew he did not. He desired all he do be done within that power but he knew it did not. (Romans 7) He was constantly reminded that he had not yet attained that level of perfection. He shared his deep sense of knowledge and personal awareness with the Philippians: "Not as though I had already attained, either were already perfect: but I follow after, if that I may apprehend that for which also I am apprehended of Christ Jesus. Brethren, I count not myself to have apprehended: but this one thing I do, forgetting those things which are behind, and reaching forth unto those things which are before, I press toward the mark for the prize of the high calling of God in Christ Jesus."When your heart is clear in analysis of your work, not your mind, then you have clear conscience and may go forward in peace. Go. Do not look behind. Press forward. Do not judge yourself. For we are far harsher judges of ourselves than He is of us.