Quatrain 9

از دی که گذشت هیچ از آن یاد مکن

فردا که نیامده است فریاد مکن

بر نامده و گذشته بنیاد مکن

حالی خوش باش و عمر بر باد مکن
 source, Dashti 54, p. 253-254

az day ke gozasht hich az aan yaad makon
fardaa ke nayaamadast faryaad makon
bar naamade wo gozashte bonyaad makon
haali khosh baash o omr bar baad makon 

The yesterday that's  gone
you must  forget what it was;
for the tomorrow not come
don't flitter and  fuss.
In the not-come and the gone
make them not your cause
Be happy just now
don't shift with the breeze.

 When Yesterday is vanished in the past,
And Morrow lingers in the future vast,
To neither give a thought but prize the hour;
For that is all you have and Time flies fast.
Saidi, quatrain 123 

Translation & Discussion of the quatrain: 
FitzGerald apparently did not use this quatrain; however, Saidi's very good rendition calls FitzGerald to mind.
1. The yesterday which has passed, do not mark it down -- Newcomers to Persian may have already noted the prefix - which can be used to negate the imperative: ma+kon.   My first experience with ma-  was in madaar -- 'don't hold/have' and I discovered this prefix through a misread; I read instead maadar - 'mother' which I tried, without success, to make fit the context. 2.  The tomorrow which has not come, do not fuss over it.  3.  Do not lay the foundation on the not-come and gone.  4.  Be happy in the present, don't throw life to the wind.  Or accurately for this idiom, 'don't throw life to the wind', don't waste your time commemorating the past and worrying over the future