Jaskier despite all the odds, was able move on without Geralt after the mountain break-up. It was hard and it took time, having to process his grief with so many moments of self-hatred and feelings of inadequacy in between... but he does pull through.
After months of traveling aimlessly, still angry, miserable and more often than not, wishing and hoping that Geralt come after him, he decided to go back home.
Teaching at Oxenfurt helped a lot... he made friends with fellow professors, taught young, doe-eyed students brimming with energy and enthusiasm. He was well liked and became the student's favorite master.
The anger lessened. And that was enough for Jaskier. He knows it won't all go away. It was fine.
He travelled in between semesters. He was a bard first and foremost and played for common folks in taverns and for nobles and royalties in lavish banquets.
He won't deny missing Geralt. And sometimes, when the night was cold and lonely, he still felt the heartache. He loved Geralt and Jaskier would not forget that. Jaskier loved Geralt for everything and was willing to give the Witcher everything the bard could give.
Their was a time when his mind was plagued by 'what ifs', repeating events on his mind and thinking of 'what could haves'. But eventually, he learned to accept it... accept that there was just one thing that happened. And there was no changing that. No mage, no entity could turn back time, change the past and change the future.
Acceptance, he thought. It was hard, no denying that.
Jaskier was no Witcher with mutation nor was he a powerful mage. He was just a surprisingly resilient human with an iron core.