At worst you've learnt something about yourself and your pitch.
At best your business has moved forward.
A friend of mine called the other day. He'd just had a meeting with a potential investor.
The meeting had gone well. But nothing was signed. Another meeting was set up.
But he was on a high. He'd received some really great feedback on his business. His meeting had reaffirmed that his business actually was a business.
So, even if the investment doesn't come through, just the extra spring in his step had made it all worthwhile.
Never turn down a meeting; good even comes from the bad ones.