I have recently started being more attentive to keeping a journal each night. While the benefits of keeping a journal have been espoused by many sources of wisdom, my particular practice is inspired by the Stoics, and takes on a certain form for a certain purpose.
In the past I have written about how we should have a sense of 'making progress' in our spiritual walk. In this effort, Epictetus prescribes careful self observation, saying that the Stoic philosopher "keeps watch over himself as over an enemy lying in ambush". Seneca likewise recommended self observation in the form of making a daily review of ourselves. Each night as we retire for the evening we should put these questions to ourselves: What bad habit have you cured today?, What fault have you resisted?, In what respect are you better? Seneca suggests that our sleep will be more tranquil, having 'sifted' through the whole day and admonished or praised ourselves appropriately. The practice of having to answer for that day's behavior will help us stay mindful and hold up in our continuous effort to make progress.
I've found this kind of review is best made in writing (or even typing/tapping). Putting this review into words makes them more real, and we can refer back to them easily if we need to. The famous Meditations of Stoic Roman Emperor Marcus Aurelius were, in fact, a journal he wrote to himself; never intended for publication.
By practicing thus, I've noticed a few additional things that are helpful. For one, I make sure not only to review what I've improved, but where I've failed. Noting the good and the bad is important. I then sum up with what I plan to do tomorrow to improve.
Finally, there is one other benefit to this review in journal form that has been quite striking. Make a practice of reading again your previous night's entry the next morning, perhaps just after meditation. This is surprisingly powerful. I think it must be because our frame of mind changes so vastly over a night's sleep that we need to be reminded of that person who existed the night before and what their concerns were. If needed, the previous night's entry can be read yet again later in the day if we need to stay on course.
If you would like to try this ancient Stoic practice, here is a checklist you might entertain as you proceed:
1) Put thought into what form your journal will take. I originally had a small notebook, but later moved to the notebook app on my smartphone because the convenience of it made it easier to always have nearby, and since I always have my phone, I could easily review it each day. Think about what will work best for you in the long run.
2) Ask: What were my most significant failures today in my spiritual practice?
3) Ask: Did I perform all the regular practices I planned to?
4) Ask: Did the traits I am trying to cultivate hold up under the day's events? (think specifically through the events of the day and if you performed as you'd preferred)
5) Ask: What did I do right and where did I make progress? (it is important to look for things to praise as well)
6) Ask: What do I plan to do tomorrow that will further improve my habits and my spiritual practice? (these might be disciplines, better adherence to practices, read/study more, work harder, better mindfulness or things such as being more compassionate, considerate, or being kinder in demeanor, and more)
7) The next morning, re-read your previous night's entry. You will be surprised how well it helps you reset your focus and stay on the path. If you need to, read it again later in the day too.
Feel free to comment on how journaling has helped you, or even come back later after trying this to report your experiences!
 Professor Keith Seddon, "The Stoics on why we should strive to be free of the passions". [LINK]