Rain, sand, gravel, and oil all reduce the available traction of your front and rear wheel. To maximize traction while cornering you must maintain a 60/40 rear/front weight distribution. Good throttle control will do this.
When cornering, crack open the throttle as early as possible and open it smoothly & consistently through the rest of the turn. This settles the chassis & gives you the best 60/40 weight distribution.
Do not chop or close the throttle!!! If you chop the throttle, the weight gets transferred to the front wheel, reduces traction to the rear wheel, and is a major cause of crashing.
Chopping the throttle also compresses the front suspension out of its useful range, making bumps in the road feel much more harsh. It also decreases the rake angle of the front fork, making the bike feel much more "twitchy" and unstable.
As far as straight line acceleration & braking, you just have to be gentler with the controls because of the reduced traction.