It just goes to show that Musk is *extremely* bad at estimating when something can realistically be completed. He's not perfect.
Maybe someone has already offered or implied this, but his practice may be his way of disciplining himself. "I've said this by such and such a time, so I better get it done." Then like other busy (80 hour work weeks!) people his focus is distracted or whatever. Doesn't bother me since my metabolic rate is near zero by comparison.