You can think of the breath as a healing process or a rejuvenating process. You're doing something positive and constructive with real results. It's helpful to work with the breath energy at a sore or injured spot.

"Find some way to get interested in the breath. It helps gladden the mind to remember that it’s working on something worthwhile. I found it really helpful when I first got into breath meditation to work with the breath energy at a sore or injured spot. It gave a sense that I was doing something positive and constructive. I could really see some results.

You can think of the breath as a healing process or a rejuvenating process. Ajaan Lee noted that as people get older, the out-breath gets longer than the in-breath, and the energy level of the breathing goes down. You might consciously try to fight aging by doing longer in-breaths and shorter out-breaths to see if the breath can have a rejuvenating influence on the body. Whatever technique you find that gives more energy to your practice is helpful. Ajaan Fuang once said, “You have to be really crazy about this to do it well.” Otherwise, you might not be paying close attention when things seem to be going okay, and then “okay” begins to get a little loose, shaky, wobbly. That’s when you have to heighten your level of involvement and focus. To get very involved in an activity, whether it’s sharpening knives or doing carpentry work, could easily be labeled obsessive; but really getting involved with your work makes you better at it.

It’s the same with the breath. You want to be really obsessed with exploring what the breath energy is doing in the body, in how it relates to the other elements and sensations in the body. When the breath seems to be going well, can it get better? When the energy level is down, experiment with getting more interested in how the meditation can lift your spirits.

However, if playing with the breath is just getting you more frazzled, that’s a sign you need to get the mind steadier. This is when you develop patience, serenity, and equanimity. Whatever comes up in the practice, you’re just going to watch it for a while, and not fiddle around so much with the breath. Give everything a chance to settle down and to do its own thing. Slow the breath down. Spread your awareness to fill the whole body, so it can’t move so easily back into the past or off into the future."

~ Thanissaro Bhikkhu "Balance & Release"