So you're recovering after a long illness and want to start playing the organ again?
That's great. I bet you feel this internal urge to practice as you're getting well since it's difficult to stay motivated when you are sick.
Yes, sometimes practice itself is a healing experience but more often than not the person will not choose to think about creativity and art unless he/she feels physically well and socially secure.
My main advice is this: Don't start where you left before your illness. You could have practiced for hours just a few months ago and your technical skills might have been quite advanced but right now, after an extended period of rest, you will need a very gradual adjustment.
If you want to reach your previous level, increase the intensity and length of your practice by 10 percent every week.
But for now, start slow and small.
The most important thing is that you'll start at all.