For your service to God to be reasonable, it must be a living sacrifice. Devil capitalizes on the unfaithfulness of a saint to tamper with his destiny. When you give what is less than your best to the service of God and humanity, it is termed "Unfaithfulness." Do your best in serving God and do not harbor any element of sin. Be a true soldier and be ready to die at your post for the sake of Christ and your professed faith.