"self-identity" is limiting illimitable!  We, human are also unknown to self and others. 
By letting go of "self-identity", naturally you unite/enter into God.

' "Concentrate on your breath, your breathing..." yes, go into yourself focus.' 
It is not going into yourself focus.  Yourself is your mental image of yourself, we call in the West, EGO.
By focus on your breath, you are focus on your natural biological rhythm. 
Thus, helping you some free moments from your constant EGO thinking. 

If it does not help, try the Centering Prayer which extracted from 'The Cloud of Unknowing'.
It suits Christian better because it focus on the presence of God with your  'gentle love' for God. 
It also help you focus on the presence of God and your love for God that if practiced with some regularity and diligence, it will help you to experience of some free moments from your constant EGO thinking!

It builds inner silence over time!