If I take a hammer and hit a flat soft sheet of medal... it creates a very NOTICEABLE dent (sticks out like a sore thumb). You could even point to where the dent IS.
However if I strike sheet of medal continuously... then I get more and more dents, and hence finer and finer detail (if strikes are controlled process rather than random). After having struck the medal a thousand or so times... we get a molded scrap of medal that resembles facial feature of Statue of Liberty. Now say I tap medal one last time for good measure. Not much a noticeable difference occurs... especially not as noticeable as initial strike! Face still looks like face; and you probably would be hard pressed to point to new dent...
Just as in "genetic code" of universe... adding more and more binary units to possibility code... 101100110011000110101001001110... we get finer and finer tuned universe (more detail and hence complexity). After trillions upon trillions of 1's and 0's... altering a single 1 or 0 near the end of the chain will not make much a noticeable difference; universe is still universe. Our most crucial choices came at beginning of chain (first few 1's & 0's), as they basically determined whether successive 1's & 0's were even logically possible. Afterall you're not allowed to choose "-" (or 0 for 'universe doesn't exist')... and then choose another number (for whether universe expands or contracts or some other set of opposite choices). How could a universe logically expand if we just told it that it doesn't exist (by choosing 0).
So sequence of 01011010... isn't logically valid. But sequence of 11011010... is a possibility and hence must be realized.
The point is Harv... if you were to have the thought that "sky is blue on Tuesdays"... That makes no noticeable difference to already UNIMAGINABLY long sequence of 1's & 0's. In other words, if you were to think different thought "sky is blue on Wednesday", who would even take notice? Sequence still looks rather similar (1001010100100...), it's just that somewhere on down the line you swapped a 1 for a 0, thereby altering possible choice (choosing one of "many worlds"). It's basically the same universe either which way. Even though there is a slight change in the sequence... there is no dramatic consequences.
"Symmetry" never made choice 1 over 0 (which caused you to have that thought)... YOU DID! You were the one who chose one hay stack over the other... just as ALL LIFE chose existing universe over nonexisting universe (of course). We simply "see" what logic (& a touch of probability) wants us to see...
The universe may have started or it equally may not have. We simply arose in one of the many different consequent possibilities of choice 1.