Stick with it dude, I'm a mechanical engineer and love my work
the academic part of engineering just gets you a job, the job then gets you the money, and the money gets you the skiing/bitches (delete as appropriate)
If you enjoy solving problems, being smart, creative and innovative to design functional products or structures or whatever it is you are working on then you're going to enjoy what you're doing too.
Engineers, doctors and lawyers have long been revered as valued members of society. Don't forget why you chose to study this great profession, take pride in your work and enjoy the results.
I get your depression - its a tough degree and really sorts the men from the boys. You'll be proud of yourself when its done and you owe it to yourself to finish what you've started.