[adouglas]

If "ride a precise and smooth line" refers to braking, then I'd say it means to avoid grabbing the brakes. Apply, then squeeze hard... as you release, also release smoothly.

The reason behind the "apply then squeeze hard" has to do with the front tire contact patch. As the weight transfers forward under braking, the tire deforms and the contact patch grows, giving you more traction.

If you suddenly grab the brake, the tire doesn't have time to do this and you're more likely to lock the front.

When you squeeze, you're allowing the contact patch to grow a bit, which then allows you to brake much harder.

One of the biggest eye-openers for me when I hit the track was just how hard you can brake. That's hard to get used to if you drive like I do... in my car I use the brakes as little as possible, for efficiency's sake.