Why is the diagnosis so difficult to accept?

I have experienced one long episode of mania.

I have been hospitalized for psychosis.

I have experienced one even longer episode of severe depression (and several milder episodes before this).

I have had multiple psychiatrists diagnose me with bipolar.

I take mood stabilizers that seem to work well.

I have no problem making the above statements. So why is it so difficult to say with conviction that I have bipolar disorder?