We often delay examining uncomfortable possibilities (religious doubts, relationship problems, etc) because confirmation of our fears would force us to confront wasted time and energy. benkuhn recommends confronting these issues because avoidance typically compounds the problem. Early course corrections, while psychologically difficult, prevent deeper entrenchment.
Staring into the abyss means thinking reasonably about things that are uncomfortable to contemplate, like arguments against your religious beliefs, or in favor of breaking up with your partner. It’s common to procrastinate on thinking hard about these things because it might require you to acknowledge that you were very wrong about something in the past, and perhaps wasted a bunch of time based on that (e.g. dating the wrong person or praying to the wrong god). However, in most cases you have to either admit this eventually or, if you never admit it, lock yourself into a sub-optimal future life trajectory, so it’s best to be impatient and stare directly into the uncomfortable topic until you’ve figured out what to do.