In every job I've ever had there comes a point within the first 6 months of my employment where something happens that just causes me to check out of the job. I go in all full of vigor and energy, and by this point I just give up and do the bare minimum.
It could be because of boring work, bad environment, terrible co-workers, horrible management, etc.
The biggest one for me was when I worked in marketing for a company whose product I was completely alienated from. The product wasn't meant for me, and I couldn't afford it with my salary even if it was meant for me. The product was also meant for people in other cities and other countries, so I couldn't even see the fruits of my labor. Hell, this product was made in another country and I never saw it in person. This product could exist or it could not exist and my life wouldn't be affected either way. Yet still I was expected to come up with marketing campaigns for this thing that I had no experience with based on digital metrics from sales and email blast clicks. It felt like playing pretend, yet I had to be serious about this weird situation.