Don't do it
It sounds strange, but if you feel overcharged and you absolutely can't find motivation or you really have to do something more important then: Don't start. This is not always possible, but it's much better than going on feverishly. Going on without motivation leads to frustration. You develop a negative attitude towards learning and this takes revenge at another occasion.
It doesn't help if you put off learning because of too little motivation. However if there is enough spare time and you just can't concentrate at that moment, it's probably better to do something else or to relax. It's much better to learn in a relaxed situation as you can keep it in your mind more easily.