As James Clears describes it in his book Atomic Habits when approaching new habits we normally go through a three-step process of results, processes and identity.
Most of us go through these steps in a top-down approach.
We first think of the results we want, like wanting to lose some weight. Then we think about our processes to achieve the desired results like choosing what diet to follow or what gym routine to try.
Only after going through these steps, we think about our identity.
Why do we want to lose weight?
Who do we want to become?
These questions are so important the we should invert the process and start with the big questions first. Once we decide on our new identity the rest is easier.
When becoming a runner I went through the steps in the common order. I first decided I wanted to run at least 5 days a week, then I settled on a plan (early mornings, Monday to Friday). Everything went well for the first few months but when things went uphill I started to find excuses like "it's raining, I better rest and go out tomorrow".
The problem was that I still saw myself as "someone trying to become a runner" rather than a "runner". So I had to invert the process, flip the switch, think of myself as a runner and focus on outcomes and processes of actual runners.
Now, I struggle less with excuses and I enjoy every single step.