Hey there, you've had lots of good advice from the others here, but I just wanted to chip in to reassure you that there is light at the end of the grad school tunnel. I'm a mechanical engineer too, and had a pretty up and down time in grad school - I think most people do. If you like your prof that's a great start, as it's often possible for them to help you refocus a project on things you're interested in. For what it's worth I now work as a rehabilitation engineer (totally different subject to my PhD) and think it's brilliant - so there are fun jobs out there, and it's well worth persevering at grad school to get there! Best of luck, Lynne.