Unpredictable Fishing

You think you have one of your local waters figured out pretty well.  Its predictable.  Right?  Not always.  And this keeps fishing interesting.  Or frustrating.  And this is where we throw in the disclaimer:
"Its always nice just to get out."  It is.  At least we ALWAYS have that.

Here's an overview of my experiences at one particular local lake over the past week:
-Trip A.  Wind moderate, fish biting reasonably well.  Caught 14 fish.  This is GOOD (but not EXCELLENT).
-Trip B.  I get a call from a buddy who says the fish are hitting on every cast.  I go.  The wind had died and changed directions.  I'm told, "You should have been here 1/2 hour ago!"  Still caught some fish (like 10), and some decent ones.  This is still OK.
-Trip C.  Relatively high wind (@15-20mph all day), usually means excellent fishing at this lake.  My buddy calls, says he caught only 3 small fish, and it was difficult to cast into the wind.  I go anyway.  I catch 5 small fish in 40 minutes.  This is SLOW.
-Trip D.  Fished during my lunch hour.  Light wind.  Almost no visible fish activity on the surface.  I catch 1 fish.  This is POOR fishing.

I keep going back, knowing the "success meter" will eventually swing in the right direction for me, but it has been declining all week.  The fact is, it changes all the time, and I know I've just not hit it during a peak moment.  Just gotta keep trying.
At least today's fish was pretty.  Its a naturally occurring hybrid sunfish: