I know I have posted Self-Actualization (SA) material at http://brainmeta.com/personality/sa.html , but thought I'd start a thread devoted to miscellaneous thoughts on the matter.  So, to begin, here are a few of my thoughts:

I don't regard SA as the 'healthiest' or 'highest state'; there are states well beyond SA that psychologists have neither identified, nor experienced, yet,   In general, I think SA is a term that's plagued with ambiguity because people understand different things by the term, partly due to the fact that one's understanding of the term is crucially dependent on one's own experiences.  Do you think someone who knows nothing about the experience of SA is going to understand anything by mere verbal definitions of the term?  The point I'm trying to make is that a person's understanding of the term 'self-actualization' is crucially dependent on that person's own SA-like experiences.  If someone hasn't experienced SA, that person will never understand what it's about.

Now, let's talk about polar opposites in an individual, without resorting to dry statements.  Consider the following polar opposites:  1) regarding everything as infinitely meaningful vs regarding everything as completely meaningless or absurd,  2) having a deadly serious temperament vs having a playful, joking temperament,  3) the experience of Being vs the experience of Nothingness or Non-Being,  4) Identifying oneself with everything vs nothing, 5) the experience of freely-willed actions vs the experience of actions beyond one's will, 6) the experience of being passionate and attached vs the experience of detachment.....the list goes on, but let me stop here.   The point is that the self-actualized individual will have or experience many of these polar opposites, at different times, but more importantly, simultaneously.  I don't doubt that experiencing polar opposites simultaneously can be a disturbing thing for some, but the reconciliation of these opposites is one of the keys, I think, to SA  because it allows one to go beyond opposites and contradictions.  One is no longer trapped within one or another 'perspective', but instead realizes all of them simultaneously.