Spock and the Vulcans were on to something. Emotions that run too high or low play havoc with your mindset and your health. Extreme fluctuation in emotions is, predominantly, too great a fluctuation in your dopamine level, the happiness neurotransmitter. This is often caused by mismanaged expectations. The key in keeping your emotions in check on a daily basis is expectations management. Keep your expectations for outcomes or the timeframe for those outcomes as realistic as possible. This keeps your emotions in check because your dopamine level will not oscillate very much if you moderate your expectations.