A major scope of personal development work is "Balance" - neither excess, nor deficit; neither total chaos, nor rigid order.
It's the same with the sense of self: the middle path is being neither fragmented, nor fused, meaning you don't want to be cut-off from your own traits, qualities, drives, impulses, emotions and feelings, nor do you want to be fused in your identity with either of those traits, qualities, drives, impulses, emotions and feelings.
A healthy sense of self is both integrated and fluid. That's easier said than done, but possible with both therapy and practice. Voice dialogue and elegant, embodied forms of Shadow work are useful and effective in developing a coherent sense of self. Any spiritual pursuits must follow this work, and not precede it: you have to have a sense of self before transcending the self.