It's always easy to say "I'll do it later", and a lot of times we then forget to do it at all. In order to make journaling a habit, we have to create a daily routine. Set a dedicated time - like in the morning right after you wake up, or at 10 PM right before you go to bed – and stick to it. It helps if you set yourself a reminder on your phone, and leave your journaling book next to your bed so you notice it when you wake up. At first you will need these reminders, but after a few days or weeks it will come very natural to you.
Of course you can journal using any kind of app or paper that is lying around, but you will take it a lot more serious of you have a dedicated and high quality notebook. Choose one that you enjoy writing in and that looks good to you - fancy, minimalistic, quirky, or whatever style you like. You will value your journaling habit a lot more and it will make it much more enjoyable.
Don't set too high expectation for yourself, you don't have to do it perfectly. It is not about forcing yourself to fill a whole page – just write as much as you think is neccessary, even if that's just two sentences! Tip: You can set yourself a 3 minute timer and just write what is on your mind until the timer goes off. When you limit yourself in that way you won't feel any guilt of not writing enough.
In the beginning it is sometimes hard to think about what to write, so a lot of people write a complete and precise narration of their day. If that's your style and you like then of course that is fine – but it does not have to be this way. Write about what you think is important, and skip the rest. That makes it also seem less like a chore and more fun, which in turn makes it easier to keep as a habit.
You are not Shakespeare. Not everything you write in your journal needs to be a groundbreaking masterpiece - in fact, nothing has to be. So don't feel bad if you don't say anything profound or deep. Never forget that you are writing this for yourself.
It is a very popular approach to follow a certain structure with your daily journal, for example to start with three things you are excited for in the coming day. If you prefer journaling in the evening you can list three things you accomplished this day. You can of course use your own promps and structure. Tip: Write down some random prompts on small pieces of paper – like "What am I most grateful for today", "What are my biggest strenghts", etc – and put them in a jar. Every day you draw a new one of the jar. With these promps you always know what to write and get started very easily.
Daily journaling is very helpful for a clear and happy mind. And while there is no wrong way to journal, there are certainly a few things that will make it easier and more fun. To make it a consistent habit, it is important to create a daily routine, which means having a dedicated journaling time each day and sticking to it. Always keep in mind that you are doing this for yourself, and nobody will be reading it (unless you want to). So let go of any expectations and just write what comes to your mind, it does not need to be profound or exciting at all. To give your journaling habit a bit of structure, you can use prompts, like "Write down 3 things I am looking forward to today". If you don't journal yet, the best time to start is today.