A way to find balance
Try to identify when you are giving something to your body and when you are asking something of it. Even just walking down the street we are asking something of our body - to walk. And when are we giving to it? When we sleep. Or when we eat. Or destress (by taking that stress away, we are giving our body peace, a calm state, a restorative state). We need to do something restorative for our body, we need to support our body, when we are asking something of it (which we always are, just to different degrees depending on what we are doing in life at the time).
Acupuncture is a restorative and supportive activity. Acupuncture is giving back to your body.
A lot of the time, what we, as the patient and practitioner, are doing is we are removing obstacles from the body so it can heal itself. The body knows how to restore itself, naturally, when given the opportunity. A really good example of this is sleep. All we have to do is lay down and go to sleep and our bodies start doing all of these amazing things to restore itself - we create more anti-bodies to the harmful microbes around us, tissue growth and repair occurs, our mind organizes thoughts and learning of the day, and so on - sleep is a process we need to stay alive. Acupuncture can put us into a restorative state, so our bodies can start doing what it needs to bring us back to balance and back to health.
Another way acupuncture removes obstacles is through a more localized route. It signals the body to bring more circulation (blood, lymph, nutrients) to a specific area of the body that is in need of that extra circulation. For example when you have physical pain or swelling, this means there is a block/stagnation/congestion in the body. Either at that specific site or somewhere else in the body. Acupuncture removes the block, it gets the Qi flowing. Let's take the example of knee pain, for this I will often choose acupuncture points right at the knee, as part of the treatment. This signals the body to start getting things moving in that area and to bring needed healing elements to that area. I might also do needles elsewhere on the body in the same treatment to encourage Qi flow/circulation through out the whole body, which will benefit/encourage flow to the knee.
A little more about the body
I also really like this description of acupuncture and how the body heals itself, described by Joseph Acquah, a founding member of the clinical staff of the Osher Center of Integrative Medicine at UCSF:
"The skin is the border to your country. And when the skin gets broken, the body sends out troops. First, a blood clotting factor gets released, so you don't bleed to death. Then there is a knitting factor that gets released to begin knitting the skin back together. Some white blood cells get sent to the area, to make sure that infection doesn't spread into the body. There is an increase in the production of cells to form new skin, we call it a scab or scar tissue. An analgesic gets released to reduce pain and stop you from going into shock. And after a day you have a little thin scab. And after a couple of days it is thicker, and then after a week or so it goes away, and we have nice normal tissue again. This happens automatically. Sometimes we look down and there is a scab and we don't even remember doing anything to cause it. So the body has done it without our thinking about it. This indicates that we have a system inside of us, that is always there taking care of us. All we are doing is tapping into that system, and marshaling it into action for you. We break the skin, but in some specific sites, that then marshals that system into action for you. That is acupuncture in a nutshell."