Doing things you don't like can make you ineffective
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this could be jobs we are not good, working with people we dislike.
When we enter a job in this frame of mind, we become anxious, irritable.
Subjective well being is a metric that basically asks us 'how are you feeling?' and if we answer 'really good!' then thats how we are.
This helps us identify tasks that make us feel (subjectively) happy and optimize for those.
We may not stop doing tasks that dont make us feel good, but we can spend the minimum time on them, outsource them, find a way to eliminate them, or plan them so that we end with a task that makes us feel good.