When I learnt to fly it was one of my greatest concerns.
Firstly stack the odds in your favour.
Way ahead of all others there are two reasons engines stop - running out of fuel and carb icing. Running out of fuel is obviously completely avoidable. Carb icing is largely avoidable but unless carb heating is used correctly (and very often it is not) it is a significant hazard. Flying injected aircraft does however eliminate this risk.
There remains mechanical failure which is either caused by poor maintenance or those very rare instances where not withstanding, something simply breaks. Engine failure due to poor maintenance is very rare (in spite of some pretty awful maintenance shops). Again even this risk can be significantly reduced by using reputable maintenance shops, having regular oil analysis and not continuing to run an engine when there are early indications of problems which may not fall foul of the airworthiness criteria but could be indicative of a more serious problem.
In summary if you are certain you will never run out of fuel, always use carb heat correctly or run an injected engine, use a good maintenance shop, have the oil analysed and never carry a potential engine problem the chance of an engine failure is almost non existent.
Having taken all the precautions engine failures divide into two types - sudden and with little warning and failures with some warning. I don’t know the statistics but I would guess sudden failures may be in the majority because one of the biggest reasons for failure is carb ice.
Failures with warning should be far easier to manage so long as you follow the golden rule of making a precautionary landing. So long as the engine is producing some power you would have to be incredibly unlucky to carry out a precautionary landing and suffer any significant damage. The problem is that pilots risk carry the problem in the hope they will get home. This is particularly true of running out of fuel. If you know you cant make a suitable airport you are far better landing in a field before you run out that have the engine quit just before you make it home.
So in a perfect world we are left with failures that haven’t arisen through running out of fuel, are not caused by carb ice, are not caused by poor maintenance, and happen suddenly. The chances of this happening are incredibly small. They are however the most difficult to manage and there is an element of luck in play.
As others have said even then you can modify your flying to minimise the risk. Here is how:
Flying high (few do) gives you so many more options - the chances are you will be able to find a suitable field and you have time on your side,
Always be aware what is around you and where you would go in the event of a failure,
Avoid flying over heavily built up areas or heavily forested areas, often skirting around adds very little to the journey,
Be incredibly aware on takeoff where you would go if the engine quit,
Always keep in your mind the direction of the wind so you can instantly set yourself up into wind,
Know the drills of by heart,
Practise engine failures regularly.
Look at fields when you drive by in your car and look at those same fields when you fly - you will form a good idea of those you would want to land in and those you would prefer not.
Finally if it all goes horribly wrong and the engine fails at 1,000 feet over a forest unexpectedly, remember that surprisingly as long as you do not panic and so ensure the aircraft does not stall, land straight ahead and have the door or canopy open you will hardly ever suffer serious injury.
Ah well, that’s what the book says, but may your God also always be with you!