Something that I say to students when I teach them forms is that you should not perform the same form more than three times on any one day. (Three doesn’t have to be the limit, but the point is don’t repeat the same form too many times.)
When I see students practising forms, I often see them do the same form over and over again, at the same speed, and without much concentration on the individual techniques. This is not a good way to practise forms – if you just repeat the same form over and over in the same way, it will become boring, and then you’re more likely to perform the form with incorrect technique. Over time you then learn the form incorrectly, and it then takes much more effort to correct the techniques.
The key to learning forms well is regular repetition. It’s much better to perform a form once a day for ten days than it is to perform that pattern ten times in one day. Regular repetition is much better for building memories. In this regard Taekwondo is similar to learning a music instrument or learning a foreign language. It’s much better to practise a piece of piano music once a day for ten days than it is to practise it ten times in one day.
Similarly, don’t always practise a form in the same way. Vary how you practise a form to prevent forms practice from becoming boring. Sometimes perform the form very slowly, or pause on each technique and check that it’s correct. Sometimes just perform the stances of the form, or practise a particular combination that’s in the form in line-work. Sometimes look at techniques in the form and think how they could be used in sparring or self defence.