Merlin Mann shares, via Steven Pressfield’s The War of Art, a quote from W.H. Murray (a mountain climber I’d never heard of outside the book):
Concerning all acts of initiative (and creation), there is one elementary truth the ignorance of which kills countless ideas and splendid plans: that the moment one definitely commits oneself, then providence moves too. A whole stream of events issues from the decision, raising in one’s favor all manner of unforeseen incidents, meetings and material assistance, which no man could have dreamt would have come his way.
I read the book a couple years ago, and while I didn’t remember the specific quote is sums up the general tone of the book quite well: just get off your ass and do something, and things will seem simpler than you envisioned on the many hours of procrastination and worrying.