The idea here is "deliberate haste." In other words, you should be in hurry to get your research done, with some sense of urgency, but you shouldn't rush yourself on any particular day. Or you can sprint on a particular day, but without forgetting that your writing is a marathon that consists of many individual "legs." The don't have to be fast if you are steady (slow and steady wins the race). Speed is a by-product of endurance, since you won't be able to write an article in a single day anyway.
If you can manage the balance between speed and slowness, you will be the master of time rather than its slave. Small windows will open up where you can get a disproportionate amount of work done. You will have free evenings when you don't have to write at all. That is why "festina lente" is one of the top 10 rules.