How to create new healthy habit and how to break old ones?

Familiarize with the formula
Cue --> routine --> reward
This is simple formula that was outlined in bestselling book The Power of Habit.

• The cue is the part that triggers the response, for example, hearing your phone vibrate would be a cue
• The routine is the response part usually the thing we perform on autopilot, in this case, that would be checking our phone
• The reward is what gives you those few good feelings, in this case, it might be distraction from work or seeing that someone commented or liked your most recent post.
  Cue, routine, reward is pretty simple formula. If you want to establish an entirely new habit, you need to come up with a cue first. Otherwise you’re not gonna know when to act and even when you do act, it changes so much from day to day, that the habits don’t tend to stick, so it’s not enough. Establishing a cue is critical to creating new habits. Eventually the routine part is going to be performed on autopilot, but in the beginning you have to work for it a little bit. Here’s a tip that might help remember that our brains are always trying to save energy, so if you’re someone who wants to pick up new habit of going for a run every morning, it can really help if the night before you set out your clothes and your shoes. Not only it does act as a cue when you see it, but it also saves you those two minutes in the morning. Decreasing the effort required to take action can really help that new habit stick.

Identify the reward
Before you even try setting up a new habit though, you need to know why you’re doing it. In other words, what is your power? I think a lot of the times people don’t pick up new habits or change old ones because the reward just isn’t satisfying enough. So identify a realistic and worthy reward whether it’s an endorphin rush after exercising or improved mental concentration after you’ve had a midday snack or a positive and happy feeling that you get after writing in your gratitude journal eventually you’re gonna start to crave this reward as soon as you see the cue, and that’s how you know the habits are starting to stick.

Breaking old habits
Breaking the old routines that we could do without. There’s a well-developed strategy that might help and it’s really simple. All you want to do is take the cue and the reward and keep those the same, but change the routine. For example, you’re someone who has a little bit of a habit of reaching for candy or chocolate after lunch every single day and you want to break that habit: the cue in this case is that mid-afternoon hunger and the reward might be both the sweet taste as well as kind of that midday energy boost you get from it. So all you want to do is change the routine. Instead of reaching for chocolate you might instead reach for some apple slices that you’ve dipped into enough butter, it’s sweet, it’s filling and it’s rewarding, so you don’t want to resist the craving, you just want to redirect it. Ensure it’s not gonna be an easy substitute at first but with repetition, it will become a habit and a snack choice that you start to crave.

Keystone habits

Keystone habits are the habits that if adopted or changed, they create a domino effect in other areas of our lives. For example, for some people, the habit of walking up early can have other positive effects on other habits, it can mean enjoying breakfast, gonna have a lesser tendency to reach for unhealthy convenient foods later in the day. It might also give them the time to work on their most important taks before noon which then increases their productivity and feeling of accomplishment. Other keystone habits might be things like exercising or writing in a gratitude journal, you can see how these keystone habits go on to influence a wider sphere of habit, it allows for small wins that gives us more courage and motivation to pick up other healthy habits as well.