When everything goes well and a habit becomes natural part of your daily routine there is the danger of forgetting it if you can't follow your routine for the day. You might skip some part of it, for whatever reason and move on. But when the habit is so strong you don't even have to think about it, you might not even think about you might have skipped it.
Even if it feels natural and you are certain you'll follow your habits every day it's still a good idea to keep track of them. Set remainders so you won't accidentally skip them.
In addition of helping you not to forget or skip the habits you get a nice log of your progress. You can also keep a count on your streaks.
There are countless of apps that can help you on this. Personally I ended up choosing Loop - Habit tracker. It's a simple tracker that let's you choose the things you wish to follow. You can set reminders on your habits. It also gives you nice data on your progress, habit strength, streaks etc. And on top of all that it's also open source!