Meditation practice is largely about building capacity in attention, but what is capacity?
- Is it how long you can rest in attention?
- Is it how strong, or deep, or clear your attention is?
- Is it well you can be in attention in different situations?
- Is it how quickly you can bounce back from a problem or disturbance?
Staying Power, stamina
The first is stability, or staying power. You develop this dimension by resting in attention. In the context of meditation on the breath, you rest in the experience of breathing. Whenever you recognize that you've been distracted, you come back to the breath and rest. Many people try to develop stability by holding their attention on the breath. This works in the short term, but creates problems in the long term because it always involves a certain about of suppression, of body sensations, emotional material, etc. It's better to rest and let stuff bubble up and resolve itself, than try to hold attention steady. Return and rest. Return and rest.
Depth, clarity
The second is clarity or depth. You develop this dimension by sharpening your attention. As you rest, bring energy into your attention. When you do, everything your experience becomes clearer and more vivid. Some people bring more attention by focusing the attention on a particular sensation or other object of attention, concentrating the attention in a way. Again, this works in the short term. Over time, however, the narrowing of attention 
can also result in suppression. You can use focusing to learn how to being energy into attention, to generate that clarity and vividness, but it's better then to let that clarity and vividness soak into every cell of your body. In other words, combine it with resting.
Versatility, flexibility
Once you have experienced stable and clear attention, you can start to develop versatility. If you are used to practicing inside, practice outside. Even on a still day, you experience subtle breezes on your face and it's a new sensation. Practice attention as you look over a field. Practice looking at a garden. Practice looking at buildings, at a street scene. Practice with noise. Start with the sounds of nature, the rustle of the wind in the trees, the bubbling melody of a small creek, the chirping of birds or crickets. Practice with the sounds of machines and of people. Learn how to rest in clear stable attention in different settings. Then practice while you are walking. At first, practice attention while you move and do things slowly. Then practice while you do the same things quickly. Practice until you can drop into attention at will wherever you are, whatever you are doing.
Resilience, recovery
To develop resilience, make a point of alternating, pushing hard and then easing off. Bring as much energy as you can into your attention and then rest in the vivid clarity. Do this for just a few moments, 10-15 seconds. Then do it again. And again. At some point, you will run out of juice, that is, you won't be able to generate the clarity. Then just rest, or go and do something else. Learn also to recognize the rhythms of practice, work deeply when conditions are right, and take a break when you feel dull, brittle, or tired. You develop resilience by making a strong effort and then taking a break before the effort creates imbalance. Balance is crucial here. Too much of a good thing is a bad thing. If you just develop staying power, you are likely to fall into trance states. If you just develop depth or clarity, it's like trying to read a book by flashes of lightening. If you try to develop versatility and resilience before you have developed stability and clarity, your attention will be weak and unstable.
When you have all four dimensions, many problems just disappear. Teachings and practices that you struggled to understand are now straightforward and clear. You understand them now because you have the capacity to do them.
