The angel lives in the heart-sphere but does not know pain. There is not strength in the love, it is something like the natural love of the infant. It is only when love is tested that love can show its strength. If it turns to hate or any emotion, that shows there was no life there. Sufis are able to experience pain in the heart without being drowned by it. The various spiritual practices are exercises to the heart-muscles and to the heart faculties. This endows the heart with life; that is to say, it enables the heart to partake of experiences and to shed the Divine Light upon them, showing the proper way through all intricacies of external existence.