Rav JB Soloveitchik tells us that what the halachah provides us with is the means of measuring our Jewish life.
We need a sukkah; the halachah defines a sukkah and specifies its proportions and measurements. We need a shofar; the halachah sets out the technical requirements of the shofar and its notes.
By means of halachah we know both the quality and the quality of the mitzvah.
The halachah of prayer, however, is different. Here the principle is not so much a measurement of quantity - how much we pray - but of quality: how we pray.
What is the rule? “A little with kavvanah (intention, concentration) is better than a great deal without kavvanah“.
This is the antidote to the High Holyday temptation to cram as many pages of the prayer book that we can into one time span, be it Rosh HaShanah morning or whatever.
Slow down, says the halachah. Focus on a prayer passage that speaks to you and to your own situation. Commune with the prayer that seizes your fancy, that grips your mind and tears at your heart. Be part of the congregation, but at the same time separate in your own spiritual cocoon.
The point is not quantity but quality when it comes to prayer.
Does this then mean leaving out the essential prayers, Ashrei, the Shema, the Amidah?
Not at all. Say them, but slowly, carefully, and with kavvanah. There’s no need to feel it’s a race or that a heavenly stopwatch is timing you.
Maybe one sentence of Ashrei will take you ten minutes. So be it. And when it comes to the added piyyutim (the liturgical poems) that expand the service, you might find yourself attracted by one and altogether unimpressed by another.
The prayer book is what you make it.