Passion can make you too close to something.
We all need to be able to step back and disconnect. In order to see flaws in the plan, respect the input of others, and maintain an open mind, a little indifference can go a long way. Passion is NOT a license to steam roll everyone in your path!
The very reason for this stems from human cognitive limits. As we all know, and as modern psychology has shown in gory detail, human beings can do a limited number of things at once, and even the best “multi-taskers” in the world are doomed to fail if they try to do too many things at once. So if you try to put all your emotional and physical effort into everything you do, you will end do everything badly. Indifference is a key survival skill as there are some things you may need to do, but are so unimportant that not caring as you travel through them is the best answer. And indifference can also help you sidestep things that seem important, but really aren’t, allowing you to focus on the few things that really matter.
In closing, let me emphasize that, on average, it is likely wiser to err on the side of caring too much rather than caring to little. Passion leads people to do great things and to travel through life caring about their work and each other — it often makes the world a better place. But indifference is worth talking about because it is something that management and workplace writers rarely consider.