‘Quran and Tasawwuf’ is a famous book written by Dr Mir Waliuddin (Allah have mercy on him). In the introduction he mentions all the various definitions of Tasawwuf by the masters of this path and concludes,

‘In view of all these various definitions by the people of the path it is known that Tasawwuf is the purification of the lower self (from all that is impermissible) and acquisition of (good) morals characteristics.’

Quran and Tasawwuf, page 14

People nowadays confuse Tasawwuf with special methods of remembrance, meditations, particular garments, dancing, trance and celebrations, etc..
It has to be made vividly clear upfront to an spiritual aspirant before he embarks on this path what Tasawwuf is and what it is not.

Frankfurt airport, to IDSA 2013