You can no longer post on Tumblr for the rest of the day/night and you have to wait till 12:00 to start posting again.
Tumblr Person 2: My life is over untill 12am... post limit ):
The post-limit is the worst possible thing that could ever happen to the common Tumblr addict. After a user posts what Tumblr finds as "too much" pictures, videos, music, etc. they will reach their Post-Limit. At first, users will usually think, "What?" and after recovering from Post-Limit Shock, they will most likely be angry. A way to bypass this is, have the user go to their settings, and change their timezone to somewhere that is one day ahead of them.