Think of what you would say to your best friend, right now, if they were going through what you are.
Make that into a short phrase e.g. 'You can do this'.
Make this phrase your password for something that you log into every day (for me, this is my work laptop).
This snippet of positive self talk, will become part of your day.
The Psychology part...
Positive self-talk doesn't always come naturally to us, it can be a hard habit to form. Often it's the negative self talk that plays a bigger part of our day.
So, by stacking this new habit (positive password), onto an existing habit (logging in), we can easily include positive talk into our day and make it a new habit, without needing to do something extra.