I came across this while reading the book 'The Power of Now' by Eckhart Tolle. It's a beautiful piece with a very simple technique. Even if you don't meditate or have never attempted it before it's okay you can still do it effortlessly. If you have the book, you can go through it yourself as well, the page number is 103.
There is a simple but powerful self-healing meditation that you can do whenever you the need to boost your immune system. It is particularly effective if used when you feel the first symptoms of an illness, but it also works with illnesses that are already entrenched if you use it at frequent intervals and with an intense focus. It will also counteract any disruption of your energy field by some form of negativity. However, it is not a substitute for the moment – to – moment practice of being in the body; otherwise, its effect will only be temporary. Here it is.
When you are unoccupied for a few minutes, and especially last thing at night before falling asleep and first thing in the morning before getting up, “flood” your body with consciousness. Close your eyes. Lie flat on your back. Choose different parts of your body to focus your attention on briefly at first: hands, feet, arms, legs, abdomen, chest, head, and so on. Feel the life energy inside those parts as intensely as you can. Stay with each part for fifteen seconds or so. Then let your attention run through the body like a wave a few times, from feet to hand and back again. This need only take a minute or so. After that, feel the inner body in its totality, as a single field of energy. Hold that feeling for a few minutes. Be intensely present during that time, present in every cell of your body. Don’t be concerned if the mind occasionally succeeds in drawing your attention out of the body and you lose yourself in some thought. As soon as you notice that this has happened, just return your attention to the inner body.
Maybe next time when you don't feel so good how about you try this out? I have tired it and it does help, but I would suggest you to do it yourself and then take a call on to do or not to do. And let me know how did you feel post doing it?