Anybody experience postpartum blues?

I had a pretty easy baby and I still felt like that at times! I had a hard time nursing and he wasn't a good eater at first, and I felt like I wasn't cut out for motherhood because I couldn't even feed my own child! Now he is a great nurser! No one can prepare you for how hard (AND FABULOUS!) motherhood is, and I find it hard to believe that there are moms out there who have never experienced that frustration!