Advice on dealing with stress as a PM

Unlike many other professions, for the most part, your stress is in your control. Not just how you manage it internally, but what you can do to address it externally. Is your stress deriving from uncertainty? Find a way to become more certain or manage the risk.

Constantly learn, adapt, take calculated risks, and ALWAYS post-mortem your mistakes. You will eventually have a big drawdown sometime in your career -- for me, it was 6 months within the first opportunity I had to manage a portfolio. Once it happens, it's imperative you step back and analyze why it happened (or is happening), whether it's a market inefficiency you can exploit long term, an investment procedure error, or a market adaptation that you now need to consider. Don't be afraid to re-position and rationalize when liquidity allows for it. 

Stress is a physiological response to uncertainty, but it can also be a great motivator in moderation. The worst outcomes happen when stress is allowed to overwhelm your rational thought or when it's suppressed or ignored to the point that the motivation to constantly improve and adapt fades away. Find your healthy balance through experience and safely pushing limits.