Journaling is a very effective strategy to figure out what part of your lifestyle is causing discomfort. I pretty much always tell my clients to journal.
My favorite suggestion is to journal about quality of sleep, mood, diet, and achiness. Diving into these topics help you realize when you agree living less than optimal. It helps you realize how often you're riving less than optimal. Once you've stayed consistent for a period of time you start seeing patterns... "When I consume dairy, I have trouble going to sleep." This is a real and common example. Once you have that realization you can start making moves in the right direction to adjust your lifestyle.
Often, my clients desire to lose weight. Big shocker, right? Well if they want to lose weight then I want to know what they're eating.I usually suggest using MyPlate or FitnessPal apps to track calories. I do a weekly check-up and usually I get a clear view of what's hendering weight loss and I can tell them to adjust accordingly.
Overall, journaling can help you figure out your goals as well as guide you to accomplishing your goals. I think every one would benefit from journaling daily. i see a difference in the quality of my life when I'm journaling consistently because I am so aware of the strengths and weaknesses of my current routine.