If you're trying to ingrain a new habit (e.g. going for a run everyday), you can create a daily repeating task for it in RTM with Priority 1 and start the task name with a special character (e.g. _Run 10 minutes).

This way it will always show up at the top of your today list so the habit doesn't fall through the cracks.

Alternatively, if you want to do this habit at a certain time of day, set a time in the due date field, and have RTM remind you when it's time.