You can do this meditation as often as you like and whenever you like.
Even if you get interrupted it doesn’t matter. It has still effected.

Imagine a bright shining light in your toes.
Now this light slowly starst to climb up filling your legbones. See them turning into shining light.
Let this light climb up further to your hip, backbone and all the way to the skull, untill your whole skeleton is made out of this light.
Now keep this image in your mind as you see how your muscles and all your organs starts to shine,
think of all the organs you can remember, also your eyes and brain.
You can do this step in an order or see where ever it starts to pour out naturally for you in this particular meditation.
The only rule of this meditation is that the direction of light is from inwards to outwards.
When you can see your whole body shining, keep this image in your mind for a while.
Then continue to see how this light forms an aura around you.
Now feel yourself inside this body and aura of pure shining light.
You can also look yourself from outside if you wish.

If you have trouble seeing yourself as light at the beginning don’t worry. Sometimes it can be felt as warmth of other way. Moving a “sun” inside may also help in the beginning. Just continue practising and slowly you’ll manage it.