Non-attachment to feelings is easier said than done. And yes, there is a place for unhappiness. But sometimes we get stuck in the unhappy feelings. Mindfulness and meditation can prepare us for these moments by teaching us to think less and to not overly “attach” to our feelings. The good news is that these skills are available for everyone to learn.
I have been enjoying the Waking Up app by Sam Harris. Here is a link for a half-off discount for the subscription. There are many other mindfulness/meditation apps, and I usually recommend trying a couple to see which one feels like the best fit for you. Many of them also have guided exercises for children.