Is My Worship Spiritual Or Merely The Effect of Natural Feeling?

How may we distinguish between the workings of natural affection, and the real exercise of grace in religious duties? This serious question recently came into my hands in these very words. Upon reading it, I could not help but see that it contained a query of the greatest importance, and therefore thought it might be very proper to take it into consideration, and give it as clear a solution as lay in my power. I confess it is a very close and interesting inquiry that requires some skill to answer it, but much more spiritual skill to apply it to our own hearts and cases. You will easily see both the importance and difficulty of the question, by stating it in this free and familiar manner.