You waited around 6-7 seconds during the prior Hagakure use.

When Hagakure is available to use, you can bottom out your Kenki and use it immediately isntead of timing it before a Sen hit.

That 6-7 seconds would have made Hagakure available a few seconds before Guren was available again.

Other than that, Kenki management is just a head game. Know when your stuff is coming up, set aside Kenki for it.