Sure, you made a mistake, but don't cut yourself up about it too much; everyone makes mistakes. What's important now is that you learn from the experience. In this case, hopefully you've learned that it's actually quite rare that you can overtake safely on a winding country road in a small car.
A few years ago, I used to commute along such roads, so I know that driving along for miles behind Mr 40mph, or even following tractors in summer, can be enormously frustrating. But stop for a moment and think: what will it actually take to get past safely? It's probably a lot more time and space than you expect.
You didn't say what kind of car you were driving, so I'll buttume it's either a typical small car -- Fiesta, Corsa, etc. -- or a slightly larger family car. Either way, the acceleration isn't going to be that great at the kinds of speed you're talking about, and it's going to take several seconds to complete the overtake. (Don't be fooled by the way motorcycles, sporty cars, and large-engined executivemobiles seem to overtake all the time on these roads; those vehicles have *much* faster acceleration at these speeds than you do, and can therefore pbutt a slow vehicle in a much shorter time.)
Now think about your safe stopping distances, and those of oncoming traffic (which, rightly or wrongly, might well be travelling significantly above the speed limit). Even in good conditions, you probably want 200+ metres of visibility *right up to the end* of the overtake, since you're going to have very limited room to manouevre while you're alongside another vehicle on the wrong side of the road, and oncoming drivers probably won't expect you to be there.
That combination of time and view needed means you're probably looking for at least a quarter-mile straight with a clear view, in good conditions, to start overtaking, and if you're driving a smaller-engined car that will take longer to get up to speed, you might need a lot more than that. Bends will play havoc with your view (watch out for "dead ground" where there's a dip in the road ahead that could be hiding an oncoming vehicle, too) so there really aren't that many suitable overtaking places on a lot of roads. All you can do is wait patiently until you get your chance to go, although often professional drivers of slow vehicles will pull off the road every few miles as a courtesy, so traffic queuing behind them can pbutt.
In poor conditions, your car's acceleration, handling and braking will all be worse, and the time and distance requirements will be much greater. Until you've got a fair bit more experience both with that car and with driving generally, I would simply recommend never overtaking in poor conditions. The kind of judgement you need to perform such an inherently dangerous manouevre will come with time and experience.
As for the back of your car spinning out, that seems quite unlikely, although to a new driver, the feeling of swerving a car with so-so handling can be very unnerving. If you're sure the back really was losing grip in your incident, you should probably get the car checked out, particularly the tyres and suspension, because it's quite hard work to spin out a car in good condition at those kinds of speeds. A lot of garages will do a routine tyre safety check for you free of charge, and as my driving instructor once told me, "It's five minutes to save your life. Are you stupid or something?" :-)
Dangerous Driving 518820 odd years ago actually. Get away with how? Legally? There were a poo load more traffic officers...
The advice other posters have given you about being too close to the car in front and so on is good too, particularly those who suggested learning to gauge your vehicle's overtaking capabilities on multi-lane roads where you can do so in relative safety before trying too much on high speed single carriageways.
Hope that helps, Chris
