Mentally. What about--
I̧͎̫͍̭͙̹̖̗̳̙̣̭̤͍̎̍̇́͂̈́ͬ̒́̒̀͊̈́ͨ͑̇ͬͮ̍̽ͯ̽͜͜͟'̷̵̮̱̪̩̻̤̻̫̻͉͙̖̩̥̿ͨ̿̅̔ͭ̓̽̊́ͦ͆̏̏͊ͨ̌ͥ̅́͘͜͟͝m̸̘͎͇͖̯̹̩̲̺͔̪̔̅͂ͤ͊̒̆̓͂ͧ̏ͤ̈́͘͢͞ͅ_͓̹͚̤̯̔͋̍́͢ so tired.
Other options:
no subject
[He broke that line of thought off for once, not the indiscriminate text corruption.
He shouldn't follow it up with anything but, well.]