Nock fit is more than a personal preference. Incorrect nock fit can be a safety concern at worst and a tuning issue at best. Here are some of the problems you may encounter with an incorrect nock fit:
Can become detached from the string prior to release, essentially causing a dry fire
Can move on the string prior to release, causing the string to slam into the nock groove on release, causing left and right groupings
Can hang onto the arrow too long and give you a false tune (arrow will act stiffer than it actually is)
So how do you know what the correct nock fit should be? There are 3 things to test once your center serving has broken in:
You should be able to slide the nock up and down the center serving (in an area where the nock set is not tied in).
You should NOT be able to rotate the arrow when it is clicked onto the center serving.
When you pull the arrow it should disconnect from the string when pulled 1/2". This can be tested by:
Place your bow square on your bow and see where your plunger button is on the ruler
Nock an arrow facing away from your bow
Pull the arrow and see how far it goes before disconnecting from the string (watch the ruler and the plunger button as you pull)
This distance should be about 1/2"
When you have a good nock fit, that is one less thing to worry about in your tuning and shot process.