Bachchan, 73, said mugging up the dialogues for the thriller is taking a toll on him.
"The relish with which films are made is a film by itself .. working on the final days of 'PINK' is a delight and a nightmare simultaneously and not necessarily in that order .. hehaha... The pages and pages of lines is well beyond human consumption for me at this moment... And so this missive is short and hopefully sweet...," Bachchan wrote on his blog.
In the film, Bachchan is playing the lead role of a lawyer. 'Pink' is produced by Shoojit Sircar and directed by Bengali filmmaker Aniruddha Roy Chowdhury.
Shoojit has teamed up with Bachchan for the third time after their unreleased film 'Shoebite' and last year's hit "Piku", which saw Big B bagging the best actor National Award.
The 'Wazir' star is the senior most actor on the sets.
"The problem with being the senior most on such sets is the belief by all else except myself that 'all shall be well'... NO... It shall not all be well .. well not until those words that float through the atmosphere of the linear shall with the juxtaposition of the haemoglobin present themselves in a less sophisticated manner to a rhetorician..!!