I don't really mind. If I eat junk food when going through stresful times, I feel lethargic to the point of just wantiong to sleep the whole time. My advice with this is, avoid junk food as stated, exercise it helps a lot, and also start stocking up on Essentiale tablets, take them whenever you start feeling a bit more tired than usual or someone tells you:"Are you ok, you look a little yellow" then there is also some liver drop from A. Vogel you can buy at any dischem, they work like a bullet, so use in extreme cases.
Why the stuff works, I don't know. Why I get tired, I haven't really researched this at all. I do the above, it keeps it in check and my live carries on normally.
PS. If you are planning on drinking, make sure you take some drops and pills, I can't really handle alcohol that well.