for me,the part of "forget thing" is about letting go of the "need of that desire",showing that you already intended and you´re letting the seed grow naturally.
that shows that you´re Trusting the Universe already sended it to you and that is already visible in the Invisible Plane.
its not really "forget like it doenst matter",its more about "forget it as let it go of the egoic need of it unfolding right away".
for example in August i manifested a huge deal: i intented this months ago and then forgot totally about it: that both my two sisters to find the love of their lifes,their true love.
suddently by no other thing than obvious synchronicities,both of them met the men of their lifes.
and i was
GOSH!!!iam really THAT GOOD!