Over time, the brain gets used to it and no longer seeks pleasure when consuming, but rather avoids the discomfort of not doing so. When the substance is missing, an alarm signal is activated that causes anxiety, irritability and a bad body. Therefore, addiction is not a lack of desire: it is a disease and needs treatment and support.
If you or someone close to you is going through this, you are not alone. Asking for help is the first step. On the RIAPAd website you will find resources to get started.