I have a difficult time writing from only one point of view. In fact, in my current WIP, I started writing in first person and quickly found myself stuck. When I opened it up to other POVs it started to move. I think knowing characters’ motivation is important and that is harder to cover without getting into their head.
However, multiple viewpoints can be a challenge. I’ve found that when I’m on a roll with one particular character it’s easier to stick to that one until I hit a wall, even if I’m skipping over chapters to do so. That way you at least have continuity for that person.
Understanding what it means to stay within a character’s viewpoint can be difficult for new writers. Bear in mind that all narrative, including the vocabulary, that relates to the POV character can’t be anything s/he doesn’t know or understand.
There are a few exceptions, but they need to be noted, such as by using a qualifying statement, i.e., “He didn’t know it at the time, but…” The main thing is not to give a character with a high school education the vocabulary of a literature professor. Unless, perchance, he’s a genius in disguise, or there is some explanation for it.
Consider your story’s point of view carefully. If you really want the reader to relate to your protagonist, the story should be told through his or her eyes only, even if you’re using third person narrative. Avoid slipping into an omniscient viewpoint by including something your character couldn’t possibly know, such as what the other person is thinking, unless, of course, he’s telepathic. Instead, describe what your protagonist is seeing in the other’s expression and body language. Another way around this you can use occasionally is to preface it with, “He didn’t know it at the time, but….” Break point of view carefully, deliberately, and sparingly.