Managing your own psychology

I remember reading post about how the toughest job of a ceo is managing your own psychology. At that time it sounded true, but no better than common sense. i.e: something that majority of the people can guess and predict. Infact i shared it with a message sharing my cynic stance. Now, at my new company, am completely incharge of a new project, and as the demo/POC day approaches, i can feel why that post is true. No am not comparing myself with a CEO of a company, but i am beginning to understand the challenges inherent in managing one’s psychology under stressful(???) nay,uncertain conditions.