Deadlines easily become an exercise in heroism. We nurture an existence that is rooted in observed reality, not announced bravado.
Deadlines: "By when do you think you'll be able to finish X?" When the addressed subject is an individual's identity, it is ego that responds.
ETA: "By when do you think, X will reach completion?" When the individual is inconsequential to the question, there exists a possibility of accuracy.