"<i>so did you padlock your backpack containing DSLR that you put on the overhead bin?"</i>

No, that thing is so big that someone will hurt themselves trying to get it out!

How much you can carry on the plane depends on the airline. Check with them to be sure if it is one bag total, one bag + personal item, size and weight restrictions.

I take multiple overnight flights per year traveling alone. My preferred method of taking care of my personal belongings is to put my 21" rollaboard in the overhead bin with everything except the items I will need on the plane + my purse. I put the purse + plane items (slippers, eyeshades, headphones, toiletries, book, etc.) in a cloth or plastic tote type bag (preferably with a zip or snap top) that I put under the seat in front of me. My small computer, camera, etc. are in the overhead bin case.

For a 1am departure, I would eat before takeoff and settle in my seat with eyeshades and headphones after takeoff (just not reclining my seat while others might be eating). I set my watch to the destination time and try to doze or sleep as much as possible for the entire flight. Every so often when I awake, I get up to make a trip to the lavatory, taking either the entire tote bag or just the toiletries, sometimes leaving my purse in the tote bag. I don't worry much about theft.

If AMS were my destination, I would get up before breakfast, get off the plane and if I could get an early checkin, I would go straight to bed "sleeping in" that morning until noon, then be very active the rest of the day. With the layover, then on to Nice, I think I would do as you plan, getting some exercise on the layover. I probably couldn't help dozing off on the flight to Nice. Just be sure to try to get to bed at a normal time that first night and even if you wake up at 3am, don't get up. Make yourself stay in bed and relax until at least 5 or 6am.

This is a simple thing, but I find that brushing my teeth and washing my face upon landing does wonders for my outlook after a long flight. If I can go straight to my hotel, I will take a shower and change clothes before going back out. If I am not going to the hotel, I put on fresh socks and underwear and deoderant as part of freshening up. Also make-up, which I don't wear on overnight flights.

I always carry a wallet around my neck which contains cash, credit cards and passport. Everything else, including camera gear, goes in cabin bag which I slide under the seat in front of me - hardly ever have to use the overhead lockers.
If you manage to sleep on the flight, lucky you!!! I can't - recently flew from Auckland to Hong Kong, leaving Auckland at midnight, so I had been awake all that day, then 11 hours to HK, in transit there for 8 hours - no sleep there - then 12.5 hours to Frankfurt. All up I reckon I had no more than 2 hours sleep in total, off and on. While in transit I like to freshen up, with face wash, teeth etc. I think by the time you arrive in Amsterdam, sure you will have jetlag, but also for me anyway, adrenaline sets in, and my faculties are there until arriving at hotel - then its time to crash. You will be fine, and running on a bit of a high.

Excellent and very helpful suggestions everyone. Thanks a lot for this.

Okay, so I will wear my money belt with me throughout the flight. And I will put a padlock on my daypack on the overhead compartment just to be safe. If my daypack is not too big, I will probably put under my seat though.

And yeah, I will also brush my teeth and wash my face before landing in Amsterdam. That usually will make me more freshened.

It sounds like you are concerned about somebody rummaging through random pieces of luggage while you are sleeping and discovering your DSLR.

That just isn't going to happen. Putting a padlock on a daypack that's stored in the overhead compartment sounds like overkill to me.

I keep my passport close to me not for anti-theft purposes, but so I don't misplace it accidentally or forget where I've placed it.