I don't think we are getting to the root cause here, clipping out should not even be an option! If you really don't think you can make it up the hill then just track your way up it. I have a buddy who will unclip and walk up hills, to me that is the biggest no-no in cycling. You get a huge confidence boost after struggling your way up a hill that you did not think you could make it up, not to mention it will make you stronger.