I asked Kamalashila that when I met him. He didn't give me much of an answer. I've been doing the Brahma Viharas for almost 25. I think going into deep meditation and meditating a lot helps. You're building on metta, karuna, and mudita, and I alternate with anapanasati, so there's building and it's a kind of culmination practice, that takes quite a lot of work to even begin trying. I think it's cool to live the questions and have meditations that don't always come easy. When I can't find metta, I work to clear out all the impediments, and obstacles. Equanimity is a balancing act, maturity, hard work. It's really one of the biggest fruits of deep practice in a sangha, with study, ethics, and devotion.