Congratulations on getting to this point – hope the exam goes well!
Things I’ve done for similar stages of life:
1) A weekend getaway – in my case, alone, but I’m sure it would be fun with a partner too – focused on spending time outside in the fresh air/doing efficient projects/adding to the “to-read” pile… One doesn’t have time for things one doesn’t have time for when caught up in studies. I found a little Airbnb cabin a few hours away from mine and had a great time not doing much. Ideally it’s good to have two nights away, this gives you a full day in between for unstructured time.
2) The short version of this – an afternoon off. One of my professional exams was in a big city with world-renowned museums – after the morning exam, I booked tickets to an exhibition in one of the museums that interested me and I enjoyed walking around, and it was fun and also kept me from mentally participating during the exam later. Also, as a treat to myself, I upgraded my ride home so that I could have drinks and snacks brought to my seat and have more space (and I read a light novel instead of studying on the way home!).
3) When I completed my research doctorate I bought myself a kayak (a folding/origami one due to my living situation – it was a slightly more expensive toy than my usual one, and I needed accessory kit (PFD, paddle, gloves, etc.), so I felt I needed an opportunity to justify it) – this also gave me the opportunity to spend more time outdoors, which I wasn’t able to do enough while I was stuck with my thesis.
4) Milestone Jewellery. Not necessarily expensive, but to make the occasion memorable. I bought myself a ring – actually I did this while I was getting over a messy break-up (he wanted to marry, I didn’t want to marry him, he was too possessive etc etc etc).
It was partly meant as a reminder that as a modern free career woman I could buy myself nice jewellery. Got this from a woman-owned small business on Etsy, a beautiful sapphire ring that wasn’t expensive for me to wear every day (about $100) but still makes me smile every time I wear it.
5) For the actual graduation ceremony, a family meal – My siblings came from out of town and we all had lunch together. It was very special because he recognized it was important to me and made the trip. But obviously one’s benefit on this may vary depending on family environment.
6) Learning something new – in a field completely different from your professional work. I took a bookbinding course, and another Kintsugi workshop – these were a lot of fun, and especially good because my exams involved mostly thinking/screen/cerebral types of learning rather than doing something physical with my hands. (I suspect that if the professional exams were practical/hands-on the more cerebral class might have been a nice contrast.) Did one of these alone, the other with a friend – both were a lot of fun.

