Like a tree breathing in CO2 and out O2, Tonglen teaches us to breathe in misfortune and breathe out goodness.
But, you object, the tree evolved to breathe in CO2 – CO2 is good for the tree. To which I respond: when plants were first evolving all they had was CO2; CO2 was all they had to work with, and they adapted to it, evolved with it. O2 came later – they breathed that out – it was their waste product. Look what happened! So today, the negativity and misfortune just happens to be what it is that we have to work with.
Life, the Buddha said, is suffering. Breathe it in. All the Big Dopamine experiences we have nowadays excite us so much, but they don’t bring contentment, much less happiness. Just trauma, really. No we must work with it, breathe in the negativity and the discontentment, and if it doesn’t kill us it will make us stronger. And then, all that goodness we are breathing out will, in time, manifest itself in widespread contentedness and lasting happiness.