One thing that I have found helpful in returning to something that I wrote some time ago is first rereading it (of course), then finding a tolerant ear (hopefully a fellow writer who can offer helpful feedback) and describe to them what the story, or chapter, is about.
That helps me to refocus on what I was trying to convey with my story, which in turn leads me to where I want to be going with it.
It also will occasionally address a problem which made me put the writing down in the first place; feeling that the story wasn't going in the right direction, or that you didn't know where it was going, or that something wasn't quite working. Bouncing your story off another writer may help you bring to the fore of your thoughts something that was previously lurking as only a vague negative feeling.
When you are writing a story from a thoroughly outlined plot, you lose the flexibility to rewrite if something just isn't working. Sometimes you have to just rip out huge chunks of your story and recreate it, keeping only those parts which are working. If you try to do that only halfway, to change midstream without rewriting what came before, then you end up with a disjointed story flow.
When I find I need to radically rewrite my work, I am reminded of a Bible quote: "And if thine eye offend thee, pluck it out, and cast it from thee: it is better for thee to enter into life with one eye, rather than having two eyes to be cast into hell fire."
When my critiquing group tells me, "yes, we know, it was a very clever and funny chapter, but it doesn't advance the plot in any way", it feels like plucking out an eye to cut out the chapter, but saying "I live this chapter too much to lose it" you may end up consigning your story to the fires of the rejection furnace.
One of the other things that helps me get back in the game for a particular story is to write a short piece from the point of view of someone other than your main character. Try writing something from the point of view of a minor character who is observing what your POV character is doing. Or something villainous which your POV's enemy is doing. Or even something which is going to be happening during the time frame for what you are about to write, but from a different perspective.