I'm sure this has some pitfalls, but since Consider and Reconsider are elements of the archetypal protagonist and antagojist, respectively, it helps me differentiate them by thinking of the elements in those terms whenever I'm feeling confused.
The protagonist says, "I've considered the pros and cons and determined this what should be pursued."
Then the antagonist comes along with information previously unconsidered. He's stronger, or has bigger guns, or kills the sidekick, or even claims he'll possesses or will do any of these things. He's saying, "Just walk away and and avoid paying the price. Reconsider your decision or it's going to turn out badly for you."
Obi Wan Kenobi asks Luke Skywalker to come with him to join the Rebellion against the Empire. Luke considers it. On one hand it's what he's always professed to want, but on the other hand, he owes a lot to his aunt and uncle, and it's the busy season, and they'll need his help around the farm. So, Luke decides to stay behind.
Then the Empire, the antagonist, steps in and vaporizes poor Uncle Owen and Aunt Beru. Luke arrives back on the farm, and this new information, these crispy bodies on the floor, forces reconsideration. All his reasons for staying behind are gone, and he now has a personal beef with the Empire, so he goes with Obi Wan to join the Rebellion.