The sole purpose of drug rehab is to change in the areas of your life that are not supporting what you ultimately want from life. If you really want to change you have to find a way to measure it, and then have an objective way to monitor it. The obvious thing that people count in drug rehab is the number of days sober, without a drink of alcohol or drug usage. The problem with this is that it is an all or none measurement. Hard to see growth and improvement with.
There are other things to measure. A depression index or mood index once a week will be very useful. As you progress in a drug rehab program your mood will lift and become more positive. External proof of this will be very beneficial on the days when you feel like nothing has changed.
You can measure your levels of fitness as your health returns. If you start working out, weight, heart rate and blood pressure can be measured at regular intervals to again show you the progress.
You can measure the number of times a day you are frustrated, or angry. As you work on developing your life skills you will see positive improvement in these areas. A drug rehab program is not just being locked away from the temptation of drugs and alcohol for 90 days. Learning how to change and how to monitor it is one of the most valuable skills you will learn in a drug rehab center.