Actually a double episode, #177 and #178, broadcast originally during May of 1994, once again featuring the relationship between the Captain of the Enterprise and the entity known as Q, and entitled "All Good Things..." Picard eventually discovers, as he travels back and forth through time, that, paradoxically, HE has created the temporal anomaly which threatens to annihilate all life in the universe.
Sorry for the double - er, triple, now - post. For a moment there, my computer seems to have entered the aforementioned temporal anomaly. Or maybe it just went nuts. Picard, indeed, expressed the same concern about himself.
http://stng.36el.com/st-tng/episodes/747.html
"All Good Things" was the best STNG episode, ever.