To be a good leader, you need to master emotions. Yours and others.
Yours, because you need to be in touch with them, be aware of them, be labelling them. And yet, you need not to be too attached to them. For example, when making decisions. In a way, you need to manage your emotions with some sort of detachment.
Others, because you need to be able to appreciate them and embrace them. You need to allocate time for others to express them, you need to be able to take them into consideration, and you need to be able to give the chance to release them.
Most leaders ignore emotions completely.
Some master theirs or others.
Few master both.