Entering a turn too fast
The first thing many inexperienced riders do when going into a corner too hot is to do everything wrong. Chopping the throttle and hitting the brakes will cause the bike to become less stable and will put more of the bike's weight over the front wheel, which is not what you want to have happen. In general, you should not brake, downshift or ease up on the throttle unless something unusual happens and you have to do that to avoid a greater problem, such as falling or running off the road.
Here are some things to do when trying to recover:
1) Use the rear brake to tighten up the line a little bit. Sometimes it feels like the right thing to do, but the real racer guys say this is not the answer because if the rear wheel breaks loose the rear end will go wide and cause you to crash (usually a highside).
2) Reduce throttle and use both brakes to slow slightly, realizing that most of the traction is being used for turning. It will slow you down, but uses additional traction.
3) Lean to the inside and continue to apply the throttle. Leaning in will cause the bike to straighten up, giving more ground clearance so hard parts don't scrape. It takes lots of courage to go faster when your brain already says you're going too fast, but often it's the right thing to do.
4) Straighten up, brake in a straight line to scrub off speed, then release the brakes and turn in tighter. Requires some room to run wider than you're already going.
The right answer is different in different situations, but the key point is that these techniques should be practiced before you have to use them in traffic.
Keith Code's book A Twist of the Wrist 2 spends about 1/3 of the book covering this question. He tends to go with #3 above. In short, staying on the throttle (you don't have to accelerate) and leaning more will help you get through the corner. Backing off the throttle makes the bike do everything wrong. Read the book. It has saved many riders from crashes.