Shiro, you are definitely one of the lucky ones. Very few know what it is to do something solely for the joy of doing the thing itself... and the great paradox is that when that is our only motivation, the 'success' that we would have wanted had we been goal (instead of process) orientated comes easy and naturally.
This is how to let the inner spark shine -- allow whatever we choose to do to be it's own reward with no preconditions or ulterior motives. What flows from that is always perfect. And what's more, somehow serendipity starts kicking in.
All great works are created from a sense of joy, not pain. If there is a 'secret' to genius, then surely this is it. Does this help answer your question tyn?