The mesh I am am making is complicated for me, so I decided to break it down into different parts as I modeled it.
The original mesh I started working with mirrored fine as I started with a plane, divided it in two, and then mirrored the deleted half.
Now when I modeled a separate object to piece together with the mesh afterwards, it does not mirror the same.
I tried making them have the same origin but it still mirrors incorrectly in all axes.
Can somebody help? Here are some screenshots.