There is a pretty popular phrase that goes along the lines of "perfect is the enemy of done"; this, of course, means that you shouldn't obsess over the details and focus on finishing your work instead of wasting time trying to make it perfect. At the same time, famous game developer Shigeru Miyamoto once said "a delayed game is eventually good, but a rushed game is forever bad"; this basically means the exact opposite: finishing for the sake of finishing could lead you to doing a bad work. What do you personally think is more important, getting the job done or making sure the job is finished perfectly?
The word "perfect" implies meeting a standard completely and I'd say meeting that standard is more important then simply getting it done. Imagine in school that you just wrote a bunch of random numbers in a math worksheet so you could be done rather then spend the time to find and write down the correct answers and get a perfect score. What do you think is going to get praise? He who is done first or he who perfectly answers all the questions?
The biggest obstacle seems to be starting it. For instance, a person can do dumbbells at home rather than go to the gym - but the motivation at home can be terrible. Also, a person can normally do homework or some project - assuming they can simply start doing it at some point and not surf the net.
I don't agree with the instructor on the movie Whiplash. I think a pat on the back is needed sometimes, but I agree some people are lazy and might want encouragement for stuff that isn't real effort and/or excellence.
Yes, the toughest thing is just to start doing it. Once you start doing it, you do the best you can and, later, simply polish up bad spots. That's the case when I'm making some jazz drumming worksheets, for instance.