I'm sorry dude, you seem like a cool guy, but unfortunately what you have said is not true. There's no such thing as talent OR success in the process of composition.
As for the rest of you all...
Massive Facepalm.
The ignorance in this thread reeks like a decaying fish.
Formal training IS necessary in the composition of art music. Not my opinion, it is a fact. All of you who are saying that Holst and Martinu and them all learned without formal training are wrong. Most of those composers that TJS listed indeed learnt composition formally, perhaps not when they were 6, but before they wrote any of their "mature" works. Now you are asking... "Why is it a fact?". Simple - By reading books you will learn all the individual components that make up a piece of music. By listening to music, you will have some idea of the conventional arrangement of these components. However, this approach is inherently flawed because you aren't writing ANY original work at this point - you're just copying what you have heard. With formal lessons, however, you will learn exactly how to arrange these characteristics into a work of art with a certain convention, and you will also learn how to arrange them in your OWN meaningful way. Thus, becoming a composer of original work.
Stop. Just stop. Stop trying to cop out of learning by assuming you can create original and highly structured music without help. You can't. It doesn't matter who you know, or who you don't know. If your music is not an original and highly structured piece of music, nobody is going to play it. It's not even about WHAT you know... it's about learning the process of original composition - something that a book cannot teach you.