Sit in a half-lotus position and close your eyes. Imagine your characters in their current states in the beginning of your scene, whatever scene you happen to be working on. Imagine where your characters are on their journey, both physically and mentally. Inhale. Exhale.
When thinking about our characters' actions, we need to understand the concept of reversible versus irreversible actions.
Reversible actions are those things that a character does in a scene that are not important enough to transport them to a different state by the end of a scene. For example, suppose your character, Stella, is on a journey to climb the Matterhorn. She's been at it for three days, and on the fourth day she drops her pack ten feet down and has to back track to get it. She does so, and a moment later, she is back where she started and ready to start her climb again. This little blip on her way is probably not enough to make or break her will. At best it was an inconvenience that is probably forgotten by the next page if not sooner. The action that she did, dropping her pack, was reversible, and she is back on course again.
In an irreversible action, the character is transported to a different state after the action has taken place. Stella is climbing the Matterhorn. On the fourth day, she drops her pack in a deep crevice. All of her food is now out of reach. Her climbing partner, Rodrigo, is looking pretty tasty. Here, we see that the action of her dropping the pack has changed her state. The stakes are higher. She's going to go hungry. She's closer to eating Rodrigo. The plot has progressed toward the conclusion of whether or not Stella makes it to the top (and back down).
Keep in mind that the irreversible action can be psychological. Your character can make a decision. Your character can come to a realization. Both of those things are valid and irreversible. Remember the first time you encountered heartbreak? Or death? Doesn't that change your life in an irreversible way? If Stella only dropped her pack ten feet and that somehow convinced her that she was not going to make the journey after all, then that act could be considered irreversible -- although, technically, I guess it's the realization that is the irreversible act, not the dropping of the pack.
In general, while reversible actions may be true to life, if you want to write a focused story where the action is continually progressing toward the climax of your story, every scene should have at least one irreversible action. Every scene should end with your character being in a different state than they were in at the start of the scene. If they only do reversible actions -- breaking up with their lover only to make up with them again -- they are not climbing that unavoidable slope up to the climax of your story. If a scene only has a character doing a reversible action, chances are, that scene can be cut.