First one can be a daunting undertaking. Not sure I remember my first one fresh out of vet school, but I'll guarantee you I was sweating it. Sure, they TOLD us how to proceed, but actually doing it yourself, without someone there to advise you...
Had more than one where I was thinking, "Man, I'm making some headway now!" - only to have the ol' heifer give a push and shove it all right back out at me. You just have to keep plugging away at it, working it back in a little at a time.
Some were quick & easy, but a lot of times, I'd be 'give out' when I got through - and covered in a sticky, gooey mixture of blood, sugar, fluid, and feces. And, it seemed like they were almost always at night, and often in cold, muddy conditions. Hmmm. Not sure I ever remember one on a nice sunny Spring day...
Had a cow that got a uterine tear one time during a really hard pull. I reached in, got a grip and prolapsed the uterus so that I could sew it up. Liked to have never gotten it back in, because of all the air that had rushed into her abdomen through the tear when I prolapsed it.