Any time you watch rnickeymouse on youtube, or look at killboy's pics, or any other motovational media, there is always a crash that is completely preventable. The "got scared, gave up, straightened out" crash. Where the rider gets spooked, thinks they're not going to make the turn, and goes straight.
We've all done it as newer riders. Come into a corner with too much speed (and probably incorrect line) and mid corner realize we're not making it (or have more turning to do). We with our primate walk/run/climb brains aren't very good at leaning and leaning too much freaks us out. Which results in as Keith Code calls them "survival reactions" like straightening out. The problem is, straightening out wont help us make the corner, and puts us at the mercy of luck once we run out of lane. Trees, ditches, rocks, woods, lawns, hills, guardrails, parked cars, all sorts of stuff you don't want to interact with is usually at the edge of the road right where we're now headed.
Do NOT straighten out and fixate on the pole/guardrail/whatever
Do NOT look at the ground, etc. You go where you look. So, if you look at the ground that's where you're going.
Do NOT give up on the turn. "jesus take the wheel" is a fine song, but not a viable riding technique
Do NOT grab the brake (it will either wash out the tire, or make you more upright)
DO NOT chop the throttle (it will stand you up, and depending on gearing and engine braking may be equivalent to hitting the brakes)
DO NOT move your shoulders to the outside. The bike angle changes the opposite direction of where you move your body. So leaning out (making yourself more upright) decreases the available lean angle, and increases the traction demands on your tires
DO NOT tighten up on the bars. If your arms aren't relaxed, you can't steer (countersteer) very well and will end up fighting yourself
Look deeper through the corner. Look deeper through the corner.Look deeper through the corner.Look deeper through the corner. You go where you look. So, look where you WANT to go, not where you're going. Look further through and you'll find yourself making the turn more often than not. Bikes are more capable than we are at turning. So let the bike turn.
Keep an even throttle, or if you absolutely must, reduce it smoothly.
If you're braking, apply brakes gradually so as to not upset the chassis.
Keep pushing forward on the bar and make the bike lean more (countersteering)
Keep your body to the inside of the turn. "underneath" the bike. Give the bike more ground clearance, less traction demands, etc.
When you STILL screw it up
the good news is, if you did everything you knew how to do and still screwed this up, you had a lowside crash. if the bike was leaned over into the corner, and you were on the inside of it, you didn't fall very far. and hopefully the bike didnt tumble after it went wherever it went. This is infinitely better on your wallet/hide than hitting stuff.
If you did get on the brakes and straighten up, all is not lost. Look back through the corner, and countersteer and make the bike turn. You're not required to go straight despite what your brain is telling you.