Unless God gives you clarity on it (and maybe he already did), I wouldn't give up on running the organization. Pray for God's guidance. It is likely that he put you into that position for a reason and perhaps you would serve him better through your work with that organization than you ever could without being in that position.

I know of one person who thought he was called to be a full time missionary when he was suddenly left with the reigns of the family business as inheritance. After praying about it, he chose to cancel his mission plans and run the business. In hindsight he says it was the greatest decision he ever made, not only did it allow him to do so much more good through the amounts of money he's been able to dedicate to God's causes through the family business, but it has also rewarded him with many opportunities to go to on missions all over the world; opportunities he would not have had if he had been the missionary he originally thought God called him to be.

If you dedicate your life and your business to God, you can do both live for him and lead the organization. You might even be able to multiply your impact through the organization.

Having said all that, if God has made it clear that he doesn't want you in that position, then he must know what he's doing.