Forming a good habit requires you to stick with it for a long period. The old "21 days" myth has been busted and it seems 66 days is the minimum you need. To keep track of that total and follow up on it, try using coloured sticky notes with numbers written on them, which you tear off with each passing day.
This plan was originally written at Life Without Bread And Butter, and adopted by The Amazing Adventures of Diet Girl blog. Both posts were written keeping the 21-day habit myth in mind, but if you're trying it, change that to 66 days.
The idea is to stick these notes in a prominent spot — one which you will see everyday. When you achieve your goal on any day, tear that note down. It's more visual than having an app on your phone to keep track, and the physical act of tearing off that note is quite satisfying, the bloggers note.