It’s best to mark your section breaks with a few asterisks rather than simply rely on an extra space, which might not be noticeable on an electronic reading device. This is particularly important if you change the point of view with the next section, a significant amount of time has passed, or the scene location has changed. Every time you leave a reader confused enough that they have to go back and reread a previous section to figure out what’s going on you run the risk of losing them entirely.