If you're still having trouble, skip ahead to examples. This may contradict
what you have been told-that mathematics is sequential, and that you must
understand each sentence before going on to the next. In reality, although
mathematical writing is necessarily sequential, mathematical understanding is
not: you (and the experts) never understand perfectly up to some point and
not at all beyond. The "beyond," where understanding is only partial, is an
essential part of the motivation and the conceptual background of the "here and
now." You may often (perhaps usually) find that when you return to something
you left half-understood, it will have become clear in the light of the further
things you have studied, even though the further things are themselves obscure.
Many students are very uncomfortable in this state of partial understanding,