Honestly most of it wasn't so bad. I took a break for a while when the initial engine build blew up and parked the truck. When I eventually got the thing back together and discovered I'd mixed up the camshafts, even that wasn't a breaking point. I just started unbolting crap, made an adjustment to the core support so I could pull the cam straight out the front, etc.
Where I almost lost it was after a couple of really long days when I went to remove the crank pulley one last time on too little sleep. Somehow I set up the harmonic balancer puller without the nose piece that centers it in the crank opening. The pulley came off, but it left a debris field of powdered metal chunks where the threading for the crank bolt used to be. That was the moment I sank to the ground and just sat there, ready to burn the truck to the ground because I didn't have it in me to pull the whole engine back out. Again.
A massive 90* rented drill, tap set, and an upsized crank bolt successfully rescued the truck from the jaws of defeat.