I was wondering why is it on my last trip to Israel I did not suffer Jet lag?

I departed NY around noon and arrived Tel Aviv around 5 AM. I was able to stay up until 9 PM and then the next morning I felt fine.

On the return TLV-JFK-SJC flight I felt fine the next day as well ? On previous trips to the east coast and Hawaii I had no jet lag as well. But on my 99 Europe trip I had it for a week.

Is this because I was able to sleep on the plane?
Drinking Coffee in the morning upon arrival?
Waking and sleeping at different times not a rigid schedule?
Eating right?
Exercising before/after flight?
Or am I just lucky?

Any ideas.?