An important element in skillfully watching tension is tremendous humility, patience and kindness towards oneself. I've found that when I'm seriously working on my edges, the challenges I'm confronted with are just beyond the range of my capacity to endure with equanimity. While it is very true that strength and stability comes from overcoming these obstacles, its also true that I stumble and fall often (and I don't think I'm alone). When I'm able to forgive myself and bring patience and kindness to my failure to be equanamous, that's the impetus to keep working with these challenges. Lack of humility, patience and self-kindness is a dead-end that stops all progress.
Anyone has seen a baby learn how to walk can appreciate the idea that if we had to take on such an analogously challenging endeavor in our adult lives, many of us would simply rule it out as impossible. How many times does a child fall before it can even walk across a room? The key is to get up and keep trying. Paramahansa Yogananda said, "A saint is a sinner who never gave up."