<p>Call it robotic, but if he's hung up on a love in the way that you seem to view it, then that would not be letting go of earthly attachments. Yes, he loved P'li, but it's a fundamentally different understanding of love than what you seem to believe. While their relationship obviously mattered to him, he was not obsesive about it. Like the mentioned fear of death, one could not be afraid of death and be at peace with the inevitability of it, but resist tooth and nail a premature death with willpower "All will die one day...but for me, not today." That would be a mixture of the two concepts working in concert. Whereas "I'm afraid to die" probably lacks willpower and certainly is not letting go of worldly attachments.
</p><p>With love, one can acknowledge that the relationship may change, one party in it may die, but that's the reality of it and becoming fixated on not losing that or dwelling on that which cannot be changed (she's dead) is unhealthy and does not help him at all in the situation, and probably actually reduces the ability to love. Also, you need to consider the fact that they were committed to taking on the Avatar and basically every world government, with little more than their merry little band. They mentally prepared themselves to die.
</p><p>It is entirely possible to love without being fixated, and that is actually very much in line with what Guru Pathik's chakra training was about and how Zaheer and P'li's relationship apparently was.
</p><p>However, and this would get into a whole topic, western romantic love is very different from the kind of love we're talking about in eastern ideas influenced by Taoism and the like.
</p>