My glib response to how a PhD works is always:
1st year work out what the hell you’re doing
2nd year do it.
3rd year do it again, properly this time.
4th year write it up.
This sums it up. Lots of the time its a slog <shudders at thought of the literature review>
I worked in industry for almost 10 years before returning to read for an MSc and then a PhD. Even if you dont work in academia then a PhD is still a good thing to have IMHO. They can never take it away with you and makes working overseas a lot easier (hence in my case the MSc and then PhD).
My blues lasted for 18 months of a 3 year engineering PhD. I was looking at novel alloys (intermetallics) and kept on getting silly results – It wasnt till I was in the SEM lab at 8pm at night after searching for 18 months that I had my Eureka moment and realised it was all down to carbon content. Freaking carbon!!!!!
Just ride and think about the topic whist on the bike – both wins!
Good luck and dont let the buggers grind you down!