It is more about the journey than the destination and all those you meet along the way. The degree / promotion / new job / [achievement] you achieve marks an end to a chapter but doesn't take away your story on how you got there. For each new chapter, accept that it may not end the way you intend. Just take some time to enjoy the road along the way. Life sometimes gives you shit (and a lot of it at times) but life will pleasantly surprise you if you keep your heart and mind open. Change is inevitable so be the change you wish to be and accept change you cannot control. Shimmering can be a good time to reflect. At least that's how I have come to terms with that feeling. I apologize if this comes off like a bad self help book, but this is something I have though a lot about when reflecting on my own life.
Sometimes the advice in bad self help books makes its way onto a page because it's good. For the record, you didn't come off that way. Let's compare my life to a car - right now, the deceleration as the transition kicks me up a gear is discomforting. I'll start cruising again soon, though! In the meantime, I'll use this shimmer for self-reflection as you suggest. Thanks for the wise words :)