How is the Anatta (not-self) doctrine useful? My question today concerns Anatta's usefulness.

What good does it bring us to realize that the "self" (what things are 
and who we are), because it is permanently changing, is therefore not real ? (that there's no "this is like that" or "I am like that" : only "this is", and "I am") ?

Personally - if this is Anatta, if I didn't get it wrong, realizing this gives me a sense of freedom (as knowing that I am born and that I die at 
each moment makes me stop clinging to ideas I sometimes have about myself).

Is this what Anatta's supposed to produce ? Not-clinging to reach Nibbana ? 

Thank you !
The 'self' is an idea/assumption born from craving for &amp; attachment to things (Parileyyaka Sutta, paragraphs 9 to 11). When the things attached to pass away (due to impermanence) there is suffering because of the 'self-clinging' or 'self-identity' with those impermanent things produces the sense of 'loss'. The Nakulapita Sutta explains this very well &amp; simply.

Therefore, yes. The purpose of anatta is to produce not-clinging to end suffering &amp; reach Nibbana. 

The Anatta-lakkhana Sutta answers your question, particularly the last paragraphs (below):


  ...all...must be regarded with proper wisdom, according to reality,
  thus: 'This is not mine, this I am not, this is not my self.'
  
  O monks, the well-instructed noble disciple, seeing thus, gets
  wearied of form, gets wearied of feeling, gets wearied of perception,
  gets wearied of mental formations, gets wearied of consciousness.
  Being wearied he becomes passion-free. In his freedom from
  passion, he is emancipated. Being emancipated, there is the knowledge
  that he is emancipated. He knows: 'birth [of self] is exhausted, lived
  is the holy life, what had to be done is done, there is nothing more
  of this [self] becoming.'
  
  This the Blessed One said. Pleased, the group of five monks were
  delighted with the exposition of the Blessed One; moreover, as this
  exposition was being spoken, the minds of the group of five monks
  were freed of defilements, without attachment.