In his classic international bestseller 'The 48 Laws of Power' Robert Green discusses how certain basic skills are required in leadership, and the mastery of these basic skills is an integral part of the development of power.
He argues the most important of these skills, in fact power's crucial foundation, is the ability to master your emotions. And indeed his research has shown that an emotional response to a situation is the single greatest barrier to power, a mistake that will cost leaders a lot more than any temporary satisfaction they may gain by expressing their feelings. Also emotions cloud reason, and he argues if you cannot see the situation clearly, you cannot prepare for and respond to it with any degree of control.
I would suggest there are two issues here for leaders to consider. The first is the need to understand the difference between 'Passion' as it applies in a visionary sense, and 'emotion'. Most organizations, boards of directors and key stakeholders nowadays often talk about leaders having a passion for what they are doing. Passion can however easily cross the line and become emotion - and cloud our sense of direction.
The second issue which can cause leaders some difficulties where emotion is concerned is the inherent human desire to be liked by people. I would contend it is dangerous for leaders to seek to be liked as individuals by the people and teams that they lead. Although this is a complex subject and probably worthy of a blog post in its own right (!) in its simplest terms it is the output and achievements of the leader that needs to be liked, not necessarily the leaders personality. If you, as a leader, are struggling with this issue you may wish to look at your emotional response to some of the difficult and challenging decisions you have to make. It may help you understand the difference.