I second what HeavyJet said. I have flown flightsim for years and it took me a long time to get the hang of things, and the fact that very small adjustments had to be made to everything. In flightsim though, you can throw the aircraft around. In real life you can't really do that (although the 747 is surprisingly manouvreable!).
Flightsims don't provide any real feedback and therefore makes things difficult. Airliners tend to be very stable compared to some of the twitchy flightsim aircraft I've tried. I always used to get bored in flightsim and come in straight at the airport 90 degrees to runway heading less than a mile from runway end. After a while I decided 'boy this is hard'. In the real thing, obviously you're not making any radical manouvres like this.
With practise comes precision and finess, be it in an airliner or flightsim.