Ah, two sides of the no sided coin ... samsara is nirvana, nirvana precisely samsara.
That's why this is Practice-Realization ... just like painting. You are an artist. Did you learn to paint in a day? Have you actually gotten better at it over the years even though each painting is one by one?
So, here is how I live this in life.
In Zazen, one experiences (A) a realm with no thought of this or that, something to add or take away, me and you ... free of conflict, flowing, whole.
And then there is (B) day to day messy life, places to go and people to see, always something in need of doing or fixing or which I wish were otherwise than what is, me bumping into you, frictions great and small, a million sometimes beautiful and sometimes horribly ugly pieces ... flowers and weeds, peace and war.
The state of wholeness (A) is lovely ... but a mistake to think that only such is freedom from Dukkha. In turn (B) is Dukkha, but it is a mistake to think it is or need only be experienced so.
So, for the experienced Zen practitioner, it is possible to learn to "flip a switch" to move mentally and physically, at will at various moments in life, between (A) and (B). Shikantaza Zazen is the vehicle that teaches us this skill. When (B) gets too hectic, ugly, fearful or any time ... switch to (A). We learn this trick.
However, in Shikantaza, one also learns another view and taste (C) ... (or better said in 'Zen Speak', Not-A-Not-B ) ... where (A) is shining right through and through (B) like the white, open, whole canvas that holds all that is painted upon it. As (A) shines in silent illumination, (B) becomes translucent ... there is a Peace of One Piece which holds all the million broken pieces of life. So, more and more one might experience, for example, a "messy life" simultaneously lit by a certain Purity which comes from dropping all thought of clean, dirty, pure or impure ... places to go and people to see, simultaneously with the experience of no place in need of going and constant total arrival ... working to make things better, stop the war and cure the diseases, even while tasting that things are just as they are with nothing to add or take away ... you and me and frictions, simultaneously free of you and me and frictions ... a Beauty and Wholeness that somehow sweeps up and holds both the beautiful and ugly ... a One Piece Peace that is peace and war and all the broken pieces ... ALL AT ONCE, AS ONE.
The canvas is there, but needs the painting to manifest life. The painting of beauty and ugliness is there, always the canvas holding all together. How to come and experience this more and more? Zazen ... Painting life, Practice.