I cannot recommend mock drafting enough. Last year, I can’t tell you how many mock drafts I did, and the only draft day surprises I got were pleasant ones, when other teams reached for players too early.
One of the main things I’ve learned from mock drafting is only draft one kicker and defense/special team. Except in the deepest of leagues, you can always find a streaming option later in these positions. You may end up sacrificing a few points by doing this, but you’ll end up with more early depth in positions that matter. Also, early season injuries or poor performance won’t kill your team nearly as much. Finally, depth in important positions can also work as trade bait later. It’s a win-win, with you on both sides of it!
On top of all that, if you create your own draft list(s), mock drafting is essential to refining your list. A good draft list means you can look at the best player available (BPA) on it, and pick it without a second thought. When you see a BPA that doesn’t work for you, maybe you need to downgrade him? Revisit your draft list after the mock draft, and knock him down where he needs to be. Or raise a better prospect higher.
Overall, mock drafting has no downside. Plus it has all the fun of a draft day, with none of the season-long risk, even as it prepares you for your REAL draft!