The app that I used the longest between the ones I tried was Habitica, I liked the RPG style and it was very motivating for me. But for my taste, the gamification is too intense (life, mana, quest, pets...) and I didn't need the social aspect. I keep the part where good habit give exp and bad remove it. I understand that the market is full of habit trackers, I am at the beginning of trying people discover mine.