First ride with bike about 95% loaded with gear...and my legs felt it

Went on a 40 mile bike ride today and had perfect riding conditions: 65 degrees and cloudy!  Normally 40 miles isn't that big of a deal for me, but today I had my bike about 95% loaded with all the gear I will bring when I go on the trip.  I had my front and back panniers both attached and somewhat filled with random clothes to add some weight.  I also threw on my tent and my sleeping bag.  Physically, that was the hardest thing I've done in a few years at least!  The good news is that I finished and the bike rode well...just heavy.  The bad news is that it was a heck of a lot harder than I thought it was going to be and didn't feel too good.  Just as I was getting my confidence up about this trip being a piece of cake, today's ride put the whole thing back into perspective for me.  Today's trip was 40 miles with a  lighter bike than I will have during the trip.  Considering I will be going about twice as far with more weight...for about 50 days in a row...I have a lot of trainging left to do!!!!!