Our natural tendency as humans is to avoid pain and seek pleasure. We go to great to lengths to protect ourselves (hide from bear) and feel good (kill and eat rabbit) - all necessary for survival in the wild. Yet not so helpful in creating the enduring happiness many modern homosapiens search for. Most of us are lucky enough to not have to fend for our survival on a daily basis. Which gifts us with time for creative exploration, and interpersonal, or spiritual evolution.
Regardless of where we are in our lives, clinging to pleasure and averting pain are unsustainable ways of being. Especially if happiness is the ultimate goal. Feeling good and feeling like shit are impermanent states, and our natural tendency to want to keep things feeling good ends up having a paradoxical effect. We chase something that is unsustainable and run from the inevitable. Happiness stems from allowing the experiences of pleasure and pain to arise and pass like clouds in the sky. Observing our tendency to cling and reject and bringing awareness to this very moment.