Sometimes in life, we attach ourselves to ideas that lead us astray. Often, the signs of having been led awry are obvious, if one is willing to be objective about his or her own situation. There is, perhaps, a struggle involved in reaching certain goals, however, when that struggle begins to negatively effect the way we interact with the world, one ought to reevalute their position.
If you're starting a business, look to the people you trust for their opinions. In fact, look to everybody, people you do and don't trust. It's a good way to gauge where you're at. While some of the greatest visionaries may have had to "prove them all wrong," more often than not, I would guess that attempting to prove everyone wrong is a indicative of denial.
I could, however, and without being a hypocrite, but maybe being in denial, say forget everything above. You definitley don't want to sell yourself short, or be upset with the choices you make. If you end up regretting the path you've taken, it might be hard to attain contentment. But consider also that if you end up with nothing due to stubborness, you might not be content either.
The point is, that it's important to follow your dream. Cliche as it sounds, do it. Seriously, do it.
But at the same time, learn to live in reality. In fact, use reality as a meter. Take your dwindling bank account as a sign you need to start earning money. Take the ill relationships with family and friends as a sign you need to evaluate your demeanor or behavior. And take the signs that tell you you're doing great as a sign to keep on truckin!