Stamina is self-explanatory. I am always in great admiration of those people, especially men, who have such energy for the tasks they are about that they never seem to fatigue, like I do so easily. I'm sure I'd get a lot more done, like they seem to, if I were like the energizer bunny. I think if I ate better and got more exercise, I could make some progress.
Emotional equilibrium required a bit more explanation. My daughter seemed to think I meant something like "lack of emotion." She (rightly) said she wouldn't want that. Nor do I.
Classical, the word for what I mean is apatheia, which one might think mean the same thing as the English word, "apathy." It doesn't, though. For ancient Stoics it meant something like "lack of strong emotions." It was a kind of indifference to what is going around you so as to be free to live a life completely ruled by reason. The emotions were seen as always the enemy of reason.
In Christian spirituality, it has come to mean that one's emotional life, no matter how intense, is completely at the service of and responsive to our rational and spiritual life. The emotions can, of course, be the enemy of reason. Some classic spiritual writers focused on this fact to the extent that they sound almost Stoic. I think some of the early desert fathers may have had something like the Stoic virtue in mind when they sought apatheia, but I don't think one can accuse some like St. Teresa of Avila or St. John of the Cross, who are undeniably spiritually advanced, of lacking in emotion. For them their rich emotional life was at the service of their intense love of God. See, for instance, Bernini's sculpture "The Ecstasy of St. Teresa."
The emotions are often like wild horses that need to be broken and tamed not so they can't run at all, but so they can run for the benefit of the spiritual soul. In fact, Gandalf's taming of Shadowfax is an excellent analogy of the proper Christian attitude towards the emotions.
Karol Wojtyla analyzes the essential role that emotions play in genuine love, especially in marriage, in Chapter Two of Love and Responsibility. The basic principle is "Mere intellectual recognition of another person's worth, however wholehearted, is not love" (p. 90). Our love is enriched by support from the emotions. The problem comes from depending on our emotions to dictate the strength and focus of our acts of love. Sympathy (primarily an emotional response) needs to be complemented and transformed by genuine friendship. And friendship needs to be bolstered by sympathy. "For a mere bilateral and reciprocal 'I want what is good for you', although it is the nucleus of friendship, remains so to speak suspended in a vacuum if it is deprived of the emotional warmth which sympathy supplies. Emotion is by itself no substitute for this 'I want what is good for you', but divorced from emotion that wish is cold and incommunicable" (p. 91).
If you haven't read Love and Responsibility, I would strongly suggest doing so, especially if you are a fan of the theology of the body. You're understanding of the theology will be enhanced considerably by knowledge of the underlying philosophical structure.
By the way, Google Books can sure be helpful if you don't feel like scrounging around in your garage to find your copy of a book when you want to quote it.