Personally, I am a master at underestimating how long it will take me to get things done. "Yeah, I can do that in two weeks," almost always turns into... more than that.
Another important thing to consider is to not underestimate the amount of progress you're making, either. Sure, the NPC may have needed work, but it's still forward progress which, in itself, is awesome.
RE: Game Development | Start Of NPC Rework