Sorry for the fall.
It could take months before you make it to 90 days... Months of work.
You can't begin to learn to run, and make a marathon 3 days later, it will just kill you.
You have to do it by little steps at the beginning. At your rythme.
The first rule of the 90 days challenge is... Don't think about the 90 days
The most important is the work on yourself, this is more important than absolutly make it to 90 days.
It's an effect of addiction that we don't see us as we really are. And also to make us great objectives that we can't reach, and to be in depression...
Take it one day at a time, stay humble with humble objectives, begin the long and deep work, and don't lose hope