"People who don't take risks make about 2 big mistakes per year. People who do take risks make about 2 big mistakes per year." Peter Drucker
If you're going to be a leader, you're going to have to take risks. That's what leaders do. In fact, I would go so far as to say that leaders are leaders in part because they are willing to take risks. This, of course, makes people uncomfortable to hear.
Risks come from taking action and leaders act. Effective leaders also understand that doing nothing can have greater risk than taking action. Especially in times of great change, sitting still can be a terrible action to take.
Taking risk and being irresponsible are two different issues. I don't care for the phrase "reasonable risk" because it is used often as a substitute for saying "Don't try anything new." Successful leaders take calculated risk. To the degree they are able, they consider the options, estimate the consequences, and then take action. If they find they have made a mistake, they recalculate and take action again.