You get peace of mind when you are aligned with your values, when you stick to your decisions, when you are disciplined, when you are committed, if you are working on your passion purpose in life. Running towards piece of mind may not always give you happiness in all situations. If you stick to your values and core beliefs and standards then it is inevitable that you have to face some rejections and disappoint others which in turn may make you feel bad.
Happiness is much simpler then achieving peace of mind because happiness is instantaneous and you can do lot of stuff at this moment to feel happy. Happiness is a state of mid and is a collection of positive feelings. For example, eating a lip smacking dessert gives you instant pleasure, drinking or smoking with friends may make you joyful for a while, watching a movie would make you happy etc. Seeking short term pleasure at higher frequency may reduce your peace of mind.
There has to be fine balance between happiness and peace of mind related activities.
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