Legacy:Travel Weariness
Traveling via teleporting or crossroads gives travel weariness, which can be removed by drinking alcoholic beverages or sleeping in a bed. Sleeping logs you out, and removes some weariness over time, while you're logged out. The amount of weariness lost depends on bed type, bed quality and time logged out.
How Travel Weariness Works
When your Travel Weariness "buff" hits 100%, you won't be able to quick travel, quite simply. The one exception is that you can always quick travel to your Hearthfire, although it will still cost travel weariness. The amount of weariness you can take is based on agility. Higher agility means you'll be able to travel farther. The amount of weariness gained when traveling is determined, non-linearly, by distance. Traveling the same distance with many small hops is preferable to one or a few large hops.
You can still choose to log in at your Hearthfire, but it will cost Travel Weariness, calculated from your last position in game.
Quoting Loftar
"With the original n00bish 10 Agility, you'll be able to travel about half a supergrid in one hop. The cost incurred by one hop scales as O(n^{3/2}), and the amount of weariness a character can handle scales linearly with agility."
Solutions
Some helpful things to reduce your travel weariness are: