I've been reading through hitoyogiri manuals from early and mid-Edo era Japan. In case you don't know, the hitoyogiri is considered to be the predecessor to the shakuhachi, and was actually called by the same name - shakuhachi - on account of its length: in this case, isshaku hachibu instead of isshaku hassun. (1.08 shaku instead of 1.8 shaku). The two share a lot in common, and I've been growing increasingly fond of this smaller, simpler (?), older flute.
From Shichiku Taizen:
Take care to follow form in terms of fingering, but don't get caught up in following a particular rhythm. You should play "ウエフエ" [a common phrase beginning many classical hitoyogiri solo pieces] without long or short. If you lengthen the next notes, then the end [of the phrase] will be short; again, if you make the end longer, then the beginning ends up short. Play so as to forget what lies ahead, so as to not know what came before. Straining to blow too hard is bad, too.
If you're not careful, this can sound like the author is saying to blow every note with the same length - but that would go against what he says at the beginning: don't get caught up in following a particular rhythm. The point is just to play the note your playing, until its finished. Once the note is finished, don't keep playing it. Don't stop it before it's over, either. Both cases are examples of dwelling on what came before or over-anticipating what comes next. You have to get to know the piece, feel how it likes to be played, and be present to it.
Shakuhachi is the same. It's about listening.
Listen to everything. When you are present as you play, even "wrong" notes sound right. It's not about how you play, in terms of techniques and specific timing. It's about who is playing. When you play, and you are listening, and you are around people who are listening, your playing changes. It's alive. When no one is listening, maybe the birds and trees are. This changes your playing, too. When no one is listening, and birds and trees aren't listening, God is still listening. When I'm not aware of anyone listening, I usually stop playing, and just listen.