I agree it can be very difficult to get started and I think to great extent it is all about momentum, and there is really no way to start the process other than by actually doing the study. Personally I find it very useful to do some exam type questions straight after having read a particular chapter - that way I'm cementing what I have just learnt.
Just recently I saw a documentary on the BBC with that Professor Robert Winston - apparently learning becomes easier if your diet contains a reasonable amount of Omega 3 a chemical often found in fish. Apparently there's a lot of evidence supporting this.