God wants believers to serve Him in truth. In fact, it is this very issue that will determine “of what sort” our work is at the judgment seat of Christ.
Strength is not tested or demonstrated during times of ease. Rather, it is during times of adversity that one finds out just how strong he is.
How would making your motive match the Lord's motive change how you approach the Christian life (from witnessing to praying to Bible reading and so on)?