S. R. Faruqi:

The word ān has the meaning of 'coquetry', and also the meaning of 'moment'. If we look at it in one way, then the verse is a playful one, in which advantage has been taken of the idiomatic meaning of mar rahne or marne ('to become a lover of'). But from this very playfulness there arises a serious paradox as well: Because if in love of the beloved it's not difficult to pass out of one's life, then why doesn't he die? His dying hundreds of times proves that dying is not difficult-- but still he doesn't die. Thus either dying is very difficult, or else he doesn't in fact want to die, but rather wants to continuously enjoy the pleasure of dying hundreds of times over her every single coquetry.

If we take it in a mystical way, then there's a suggestion of the mood of dying in every single moment and rising up alive again, like 'those slain by the dagger of submission'. It's well known that at the time of the mystical-hearing [samāʿat] of the following [Persian] verse, Hazrat Qutb ul-din Bakhtyar Kaki gave his life into the care of the Lord:

kushtagān-e ḳhanjar-e taslīm rā
har zamāñ az ġhaib jān-e dīgar ast

'For those slain by the dagger of submission
At every moment, from the Unseen, there is another life.'

The true lover presents his life in the service of the beloved at every moment, and at every moment a new life is bestowed upon him.

FWP:

SETS == DOUBLE ACTIVATION; KYA
MOTIFS == LIFE/DEATH
NAMES
TERMS == PARADOX

The excellent multivalence of kyā reinforces the paradox of which SRF speaks, for mushkil hai kyā can of course be read in three ways:

=is it difficult?
=how difficult it is!
=as if it's difficult!

In the second line, the idiomatic 'to pass out of one's life' [jān se gużarnā] is a nice touch, because it evokes the Sufistic style of passing out of one's 'self' and thus becoming 'self-less' [be-ḳhvud]. It also has a flavor of volition, since gużarnā is a verb used in the ordinary course of life (with it one can 'pass by', 'pass over', 'pass through', 'surpass', etc.). The English idiom 'to pass away' isn't as vivid, so as usual I stuck with extreme literalness.

The attribution of sau sau deaths to ek ek ān has the additional pleasure of what I call 'double activation', since the two meanings of ān (see the definitions above) are both fully invoked in the verse. The sense of 'moment' is perfectly suited to a hyperbolic shortness of time, and the sense of 'coquetry' is perfectly suited to the hyperbolic potency of the beloved's charms.

Compare Ghalib's take on the same paradoxical life-in-death of the lover:

G{164,8}.