The zealous display of the strength of their belief, while the judicious show the ground of it. – William Shenstone, eighteen-century poet and landscape designer.
Being a Crusader does not pay either. Every once a while, you will find an idea so fascinating it becomes hard to think about it objectively. The stars align, heavenly trumpets blare, and suddenly you have a distinct impression that you have found your calling.
In all the excitement, it is easy to forget that there is often a considerable difference between an interesting idea and a stable business. In your optimism, do not forget your prudence: changing the world is difficult if you cannot pay the bills.
Some ideas do not have enough of a market behind them to support a business, and that is fine. That does not mean you should ignore them: side projects can help you expand your knowledge, improve your skills, and experiment with new methods and techniques. I am a massive advocate of pursuing side projects as long as you do not count on them to reliably produce income. Once you have your financial bases covered, crusade all you want.
Before attempting to launch a business, take the time to do a thorough evaluation using the Ten Ways to Evaluate a Market. If you are finding it difficult to be objective, see a trusted colleague or adviser, then test it as quickly and as inexpensively as you can before you fully commit. A few hours spent in evaluation can prevent months (or years) of frustration and misplaced effort.
This concept by the author: http://book.personalmba.com/crusader-role/