If you are trying to find an agent or publisher, don't define success just as landing one. If that's your definition and it takes 200 days, 199 of those will feel like failures.
Instead, define success as your unrelenting effort to move toward your goal (while learning from the strategies that are not getting you there yet, too).
Writing an excellent query letter is a victory.
Researching which agents might be a good fit for you is a victory.
Sending your query letter to as many as it takes is a victory.
Writing a good proposal or book or screenplay is a victory.
All those things are the cake. Getting the agent or selling the book is the icing.
(for more support, get my book, "Your Writing Coach," published by Nicholas Brealey and available from Amazon and other booksellers.)
