The game gets faster, the talent level is higher, teams make adjustments quicker and more effectively than they've seen up to that point.
If you get complacent, no lead is safe.
And that's what a young West Virginia team found out the hard way in Tuesday's 87-82 loss to Virginia Tech in Blacksburg. Little by little, the Mountaineers saw their 17-point lead in the first half slip away.
They got comfortable.
In its first road test of the season, against a Hokie team that is probably going to be among the bottom of the ACC this season, West Virginia learned a lesson Bob Huggins had been trying to teach them all preseason the hard way.
"As much as you try to tell them and tell them, they've been the best player on their teams so they've been able to just take the ball and do what they wanted to do with it," Huggins said. "I've got a whole bunch of freshmen that don't understand how hard they have to play.
"It's like with your kids, you try to do the best job you possibly can at telling your kids what's going to happen. Most of the time, they don't listen to you, but you've already been through it. You try to say, 'Don't make the same mistakes I made,' and they just go do it."
For the players, they feel that it all comes down to knowing what your job is and committing yourself to going out on the floor, playing hard and not taking any lead for granted.
Of course, it's easy to say those things, but sometimes young teams can have a difficult time playing at the level it needs to because, as we saw Tuesday, when things are going really well. Good teams won't have a problem with that.
Tuesday, West Virginia proved that it's not at that level quite yet. After an impressive performance against Mount St. Mary's to begin the season, this was a good measuring stick to see where the young Mountaineers stand.
And they didn't pass the test.
But that doesn't mean it's all bad.
While I'm a strong believer that there aren't moral victories, West Virginia kept fighting once it blew its big lead and Virginia Tech began to pull away.
If last season's team had been in a similar situation, where it had a big lead and then the other team got hot and in the blink of an eye had a double-digit lead of its own, it would have crumbled. To their credit, this year's Mountaineer team didn't do that when it had the chance to.
It doesn't make up for the fact that they shouldn't have had to mount that sort of comeback in the first place if they would have just done what they needed to do and keep up the intensity for all 40 minutes, but it's something they can learn from.
Even if Huggins doesn't necessarily want to see them take a loss to have to learn those lessons. But could you blame him? With a daunting schedule like WVU has to face this season, it can't take any chance to come away with a win for granted.
Wins will be tough to come by in a talented Big 12 Conference this season, and they need to win games against teams that aren't that good - like Virginia Tech.
But they blew it, and they'll have to learn from it.
And I guess you expect that with a young team.