Get enough sleep. I found that days when things really felt like they were falling apart, if I took a break and slept in the next day it was WAY better. This meant that I sometimes missed morning rounds or only got to hold her once during the day instead of twice, but it was better than sitting there for hours seething and anxious and falling apart.
Maybe this doesn't work for everyone-- but if the doc says not to worry about it, then don't. We have a problem in this country of OVER testing and OVER diagnosing (especially with these more straightforward medical issues) so if they are UNDERwhelmed by what they see- then let it go. My DD had a Grade 1 bleed. It was of no consequence and I have never heard anyone say it went badly for them. You will have plenty of real things to worry about, like paying for college and your great aunt with a cold visiting you and night time feedings once they are home. The docs are not lying to you so take advantage of their reassurance. If anyone did a head to toe ultrasound/ CT scan/MRI on YOU, they would probably find all sorts of weird things in there.
Another thing to consider is that we often think of "postpartum depression" but often that really shows up as postpartum anxiety. Which needs to be treated with supportive people around you feeding you, letting you sleep, pushing you to go for a brief walk on a nice day, and talking to your OBGYN/midwife/primary care provider about it.
--especially the sleep and anxiety. :(
And just to help ease your worry--I have a cyst in my brain. I was told that in this day and age, most of them are found by sheer coincidence or accident while looking for/at other problems. In your case--probably in investigating the bleed... kwim? Mine was found while investigating a 9-day long migraine that rendered me unable to drive (I had migraines a lot back then) but they didn't even attribute the cyst to the migraine (and they were correct). I don't recall the why of it now, but I know that my scans had to be reviewed by a neurosurgeon to be sure I was okay and they had me do an MRI every year for 5 years (I was in my early 30s when they found it). My migraines wound up being "cured" a few years later through chiropractic therapy. I still have the cyst with no issues.