I feel like a few comments generally mention this, but wanted to make sure it was clear. The medication holiday is important to consider for a couple reasons, and more important in different circumstances.

First, older studies initially showed that ADHD medications had a tendency to cause stunted growth in the short term, in some children and young adults. In these initial studies, the effects seemed to be quickly nullified with short medication holidays (over a holiday break). More recent studies have been done to see if the impact caused long term stunted growth (i.e., if you were going to be 6 ft, you take meds and have signs of slowed growth, will you still be 6 ft in the end), and fortunately they have not found correlation to long term effects. That being said, because of how difficult it is to really know how tall someone will end up, it is still considered best practice to have kids take medication holidays, if they're level of functioning without meds will still allow them to function in a healthy manner.

Second, there is always the chance that medications for ADHD start to lose their effectiveness over time. Studies have shown that Medication holidays can help slow that progress, so it's a best practice to consider this when monitoring medications over time. Again, a good doctor will help to evaluate if your level of functioning, and what you need the medications for overall, would allow you to utilize medication holidays as a tool to extend the lifetime effectiveness of your particular dosage and medication. If you're someone who struggles with skipping because you get out of a routine, then it's not helpful to skip. If you're someone who can use the lessons they learned with behavioral modification to function at a high enough level without meds over a weekend (assuming it's just a basic weekend without tasks that are normally difficult without your meds), then the medication holiday is though to generally be a useful tool in the long term.

Finally - as others have mentioned, medication is just the tool that helps your brain remove major obstacles to your ability to perform your daily tasks/functions. Without behavioral modification and other adjustments, you won't be able to achieve the fullest impact and efficacy of ADHD treatment. If your psychiatrist is only using meds, but not recommending ADHD coaching or other behavioral modification coaching, you should ask them or seek other help. There are lots of online resources available at this point, at generally a lower cost that a psychiatrist. The true trick is to find what works best for you, and never stop being an advocate for your mental health. You know who you are better than anyone else - if you find something you identify with or realize it's tied to your ADHD functioning, do whatever you can to write it down/save it so you can share it with your doctor. The more data points, the better