Let's break the Gravity Tax down into three simple steps.
1. Gravity pulls fluid down all day.
Every hour you spend standing at a counter or sitting at a desk, gravity is pulling fluid down toward your feet. That part never switches off.
2. Tired valves let it pool at the ankle.
The one-way valves inside your leg veins are supposed to snap shut and stop fluid sliding back. When they're tired, they don't close as well. So a little more fluid stays behind every hour.
3. The vein wall stretches, so your legs feel heavier by evening.
As fluid pools, the vein wall stretches. A stretched vein wall makes it even harder for the valves to close. It's a loop, and it builds all day long.
That's why your legs feel fine in the morning and heavy by 5 PM. It's not random. It follows your clock.
Now look at the usual fixes again, with this in mind:
Compression socks squeeze from the outside. They push fluid up while they're on. The moment they come off, the vein wall is still stretched and the valves are still tired, so everything sags back.
Cooling gels cool the skin. They never reach the vein underneath it.
Massagers shove fluid around. The valve stays loose, ready to let it pool again by dinner.