-The sleep hygeine recommendations are excellent overall. However, the recommendation with naps applies more to people experiencing insomnia (I think). Naps, applied correctly, are well-proven to improve efficiency during the day (we're talking scheduled, 20-40min naps between 1-3pm here).
Of course, given that your problem is too many naps, it may be a good idea to avoid them entirely, at least until you get them under control (and that may be exactly why carigallen recommended against naps).
-Getting your eyes checked, as mentioned above, is also a good idea, especially if you are having a hard time concentrating on text and/or are experiencing eye strain/headaches
Additional comments:
-Getting too much sleep can also be fatigue (and depression, incidentally) inducing. Most people need in the range of 6-8 hours of sleep a night (with 7 being optimal for longevity, epidemiologically speaking). So getting less than 6 or more than 8 might be a problem (keep in mind there is variation among people, so these exact numbers may not apply to you). Balance is key.
-No matter what your sleeping habits are like, you may become drowsy if you are extremely bored for extended periods of time. This can occur during studying if 1. you despise the material, 2. you don't understand the material and can't get a handle on it, 3. aren't studying actively enough, or 4. are studying for too long without breaks. So, make sure that:
1. You don't hate the material (I presume this isn't your problem).
2 & 3. You are understanding and integrating what you read. If you aren't making connections and understanding things, it's just like forcing yourself to read Latin or Portuguese (assuming you don't speak them), and about as interesting. Also, sometimes you can read and understand individual sentences, or paragraphs, but if you can't integrate that information with what you already know, it's similarly uninteresting and you'll forget it besides.
4. If you're forcing yourself to stare at the same book/notes for hours on end, you might just need to switch subjects more often, and/or take short breaks. I heard recently from a psychology student that the most efficient way to study (for pure memory efficiency) is for .5 hours followed by a 1.5 hour break (then reapeat). Now, we all know that strategy is patently impossible to apply for medical students (not enough time in a day), but keep the principle in mind. Take a 10 minute break occasionally to walk around. Talk with friends for a bit, whatever. Again, this is a balance.
That's all I can think of for now. Best of luck.
My best advice: try lots of things, and do whatever works for you.
because the steady beat and repeating melody let's you focus.
