(A Course in Miracles)
Self-Improvements is a strange concept. Your "Self", i.e. your soul connection to God doesn't need any improvement, so it must be the "self" we are talking about, i.e. our behaviors and personality. Can you really get the self closer to your Self by actively trying? You can become more polished, perhaps more targeted and potent with steady practice, but can you actively become more loving, which is the hallmark of spirituality?
The self-improvement guru Anthony Robbins writes: "Each day we must strive for constant and never ending improvement". Sure, you can try to, but I would worry that the ego becomes stronger that way. Don't get me wrong, the intent of spiritual advancement, of getting closer to God is a good one; but you do that by letting go instead. Spirituality is a perception. When you experience strain, you may want to abstain. But when you recognize love and care, make sure that you go there. Spirituality is the art of recognizing Her in action; and once you do, there is nothing else to improve upon.