I have Sun at 13 degrees Gemini (9th house), so I had this transit last year, first direct at around February/March, and then retrograde at around Christmastime.
My Neptune is pretty powerful. Conjunct the IC and opposite Mercury/Mars on the MC. Neptune and Sun are aspected by declination only, closely contra-parallel.
Nothing major or life-changing happened during those times, or inbetween, or in the times before or after. I was very creatively active (art, photography, music), got into astrology again, had slight changes to my workplace and work schedule, did some traveling, lost my main online creative venue because of corporate greed, had some minor medical issues, and fell in love with my mum's new puppy. But that's pretty much it... As far as mental state goes I don't remember there being any extra confusion or fatigue. Overall it was a period of status quo, creativity, and blissful enjoyment of the little things in life. I don't know why, but transits don't tend to impact me much, and this one was no different. I also had Saturn transiting the IC at these same times... and yeah, didn't notice that one either.