Shaykh Sayyid Zawwar Hussain Shah (Allah have mercy on him) said,

‘The progress in spiritual path (sulook) is not sudden.  It is gradual and therefore, not appreciated by the spiritual traveller.

For example, if someone has hundred rupees in his pocket the addition of one more does not draw any attention and is, therefore, most of the time  not appreciated.  However, when this addition increases to two hundred then the increase is evidently appreciated.

In most of the instances the spiritual aspirant can not gauge his own progress. The Shaykh, however, assesses this by various signs and symptoms and leads him further on the path. ‘

Mahnama Tamir e ifkar, eshaet khas bayad Shaykh Syed Zawwar Hussain Shah (Allah have mercy on him), page 596

Shaykh Syed Zawwar Hussain Shah (Allah have mercy on him) was born in a Shiafamily. It was after correspondence with Hakim al-Umma Shaykh Ashraf Ali Thanawi (Allah have mercy on him) he became a Sunni.