Unless you’re about to retire, it shouldn’t matter. As long as you’ve been dollar cost averaging every month and buying more into it, you’ll be in a much better position when you do retire. The market is always going to cycle up and down (over long term) and you just need to deal with it.

And if you’re close to retirement and seeing large changes due to to market, you haven’t invested properly. The closer you are to retirement the more safe the investments should be.

Checking your 401k balance every day at 30 years old is going to make you crazy.