In my life as a small business owner and software developer, I have always benefited from an outside yet honest opinion. No topic is off limits. Discussing your successes, your failures and your plans (think future successes and failures) with someone who may not share your opinion is tremendously enlightening. Your idea of a failure may be considered a break even proposition by another. Your idea for a great new marketing plan may be tempered by someone who's tried it before.
In business, I regularly ask a CPA, a Creative Director, a Cabinetmaker, a Doctor and other small business owners I know for their opinion. Often times, I discover that they have similar experiences or second hand experience that they can share. This might cause me to rethink the scenario or do additional research on the topic. Words of encouragement never hurt either.
In software, I have to solve new problems every day. Sometimes the problems are logical, sometimes they are simple human relations. Taking a few minutes to step back then trying to explain the problem to another will, more times than not, provide the solution. If you can't explain it well to someone else, you will know that you haven't properly defined the problem.