poem in NYC Subway...

I was on the 6 train yesterday and started looking at all the ads on the top of the subway car, one of the ads had a poem, which I found interesting:

If there is something to desire,
there will be something to regret.
If there is something to regret,
there will be something to recall.
If there is something to recall,
there was nothing to regret.
If there was nothing to regret,
there was nothing to desire.
-Vera Pavlova

I'm still trying to figure out what the poem is trying to get across because it seems that there are contradictory statements between the 2 parts of the poem which talks about the future based on the present and one which talks about the past based on the present, yet they seem to contradict each other, am I missing something here or am I just not able to figure out the logic in this poem?