IKEA effect
The tendency to value things more highly when we have helped build or create them, even when the result is imperfect. It is named after the furniture store whose products buyers assemble themselves.
In everyday life
A person values their wobbly homemade bookshelf more than a sturdier store-bought one.
At a cooking class, you rate the pasta you made yourself as better than the chef's, even though your sauce is clearly lumpy.
Why your mind does this
Finishing what we start is usually a good strategy, since a brain that quit at every bump would never complete anything. Valuing what we already have, what we built and what we worked for keeps us committed and protects our resources. Losing what we have can hurt more than an equal gain helps, so caution around losses often makes sense.
How to spot it
Ask whether you would rate this as highly if someone else had made it.
How to counter it
Have someone who didn't help make it judge the quality before you decide how good it is.