In reading this book be very certain you never go past a word you do not fully understand.

The only reason a person gives up a study or becomes confused or unable to learn is that he or she has gone past a word or phrase that was not understood.

If the material becomes confusing or you can't seem to grasp it, there will be a word just earlier that you have not understood.  Don't go any further, but go back to before you got into trouble, find the misunderstood word and get it defined, using any good dictionary.