The problem is, assuming the butterfly effect, anything you change could trigger the paradox -- and the further you go back, the less work you need to do find a trigger.

I mean you can't even cause the timeline in which you decide to go back to change; your memory would either have to be altered to match [a paradox: which memory was "first"? Neither] or you'd have a memory from a timeline that never existed [does that count as a paradox?]