To put it plainly, taking a plane is bad for us. The less the better, and yet most of us often travel for work and/or leisure more than we often want to. Cold, insomnia, bowel disturbances and energy crashes being the most common denominators, none of them are welcome at any time, but are easily combined when traveling.
I learned to prepare and plan early on in my career and applied the basics of pre and/during/post tips all my life to avoid the imbalance (for body and mind) that air travel causes: