Have you ever tried to go cold turkey with caffeine or similar? The headaches, the run down feeling and general ickiness you experienced is much like the so-called "low-carb flu" that many suffer when dropping their carb levels significantly over a short period of time.
While it isn't particularly pleasant this feeling doesn't last forever and is worth the effort if you are looking to drop your carb levels for health and fitness reasons. This cleansing as it were, or the process of your body adjusting to working in a different way is significant. It is also part of a larger metabolic cycle.
The flu-like symptoms you may experience when dropping to a low carb diet include low-grade headaches, a general feeling of tiredness, lack of energy and similar, hence why it is likened to flu. What is actually happening here is that your body is teaching itself to find a different way to fuel your systems rather than depending on the sugar/carb conversions it has found easy to work with in the past. The bad news is that the transition period (and therefore the symptoms) may last anywhere from two weeks to around six or seven. the good news however is that after this time your body will get used to burning fat for energy instead.
We are all born with a genetic make-up, something we can't alter as such however there is evidence that rather than change our genes we can coerce and train them into doing what we want and this process is one example of this. We choose to force our body into changing how it works so that it might fuel itself differently, offering up a wealth of health and fitness success as a result.
Once your body has adapted to the change you will have become uber-efficient at burning fat, as this is what your body is now programmed to do. This might sound like something that belongs in a Star Trek medical bay however it does work. When you train your body this way you are effectively muting or turning off the genes that have been taught or are programmed to convert carbs into energy by default and activating those that look to convert fat instead. Your body will work just as well on fat-fuel so there is no concern regarding a reduction in performance etc.
This might sound very technical but from a grass-roots perspective all that you need to do is to commit yourself to the low carb lifestyle and look at how you exercise a little differently. A short burst of intense activity for example will not help you burn fat for fuel however a longer session of low to mid intensity exercise will. Facts such as these are why it is important to work to not only a dedicated and individual fitness plan but also a nutritional one that will back you up and make sure you have what you need in order to meet your goals.
To help with the carb withdrawal ensure that you look after yourself otherwise, including hydration and ensuring your additional nutritional needs are maintained. Natural supplements may help however if you feel the symptoms are too much to handle considering your busy lifestyle increase the carbs to a "better" level and then drop them again more gradually.