If a newbie was to ask the same questions as you, most of us would say "Grow up slowly and enjoy the ride." But you have done some extra heavy hauling. I did too and carried the load at way over the limit for the GVW without issues.
But when I went to the fifth wheel and had 9000 pounds pushing me downhill, that was a different story. No way could I use my brakes to slow me, so I could only ask my gears and engine to slow the entire rig. Some of the hills here can be seven miles long.
My 7.3 diesel would still do 50 mph in second gear on a steep hill, and when I got into the skinny roads that's way to fast. First gear was necessary to hold back the rig.
Be prepared to do the same, but you will pull it fine and tow it easily, just not stop as easily as some.