I've found that I put things off whenever I can do so without immediately paying a price for it. When time pressure increases at the last minute, I have no problem motivating myself - but of course that's not ideal for a variety of reasons and sometimes results in a reduction in quality.

Creating artificial pressures that can't just be disarmed acts as a motivation amplifier for me. It's something like setting an alarm clock that's sufficiently loud and unpleasant as to make sleeping through it not worthwhile, and placing it out of reach so that it can't just be turned off without getting up.

Disciplining the undermind is difficult, but very important. Set up costs for not starting projects at the proper time and ensure that you'll pay them - either by enacting will or by enlisting external agents to help.