How I understand from what I have read in many posts, most people seem to see the two lines going hand in hand. what I mean by that is they see the lines playing out together -
Nafrat paas aane na de! Mohabbat Door Jaane na de,
So to most it means that whenever there is a reason for hate to come up, it will tear them apart but the flame of their love will not be able to go away from each other completely.
The issue I have with this interpretation is that in this case, the story will always been running in a spiral, stuck in the puzzle of nafrat and mohabbat again and gain, swaying between separations and reunions, which doesn't seem like an interesting prospect in terms of watching to me.
And if we really rewind and recall, Arnav and Khushi have never really been separated. They were together, though forcibly, when they hated each other, so now when they love each other why will they be separated.
Anyways, let me share how I have understood this tagline. Yeah I am allowed to interpret too 😉
For me its a journey... that starts with hate and ends with love. When it all began, they hated each other and that was the cause for them always moving away from each other. So that is the Nafrat paas aane na de!
The journey that began at the fashion show, instantly resounded in hatred for both. This caused them to run in opposite direction whenever they met. They couldnt wait to get away from each other, be it the accidental collision, working in the same office space, Khushi coming to train Lavanya.
Their hatred didnt allow them to be in the same soace...even when this softened, the misunderstanding happened and it rekindled the hatred that kepy them apart inspite of them being married.
The journey up until now focused on Nafrat paas aane na de!
Then love happened and it grew and is still growing! And this love is what will prevent anything or anyone keeping them apart, so their mohabbat will not let them move apart!
Which is what we are witnessing now, circumstances and people trying to create a rift, be it Anjali's attempt to harm herself and Arnav loosing his cool over it, Khushi bringing back Arnav's arch nemesis back into the house, Garima's impending revelation, Shyam and Daadi's plots and schemes. They have been able to overcome most of the above hindrances and obstacles that could have easier torn them apart giving to their character and nature. But the only reason they survived them (and I hope they will survive the upcoming storm) is because of their love. Unki Mohabbat Unhe Door Jaane nahi deti hai.
So basically what started with nafrat is ended in mohabbat, the person they didnt want too live with, has become the person they cannot live without.
So I dont see it as two things that go hand in hand but as a journey, the half mark of which we have reached!!