I kinda agree. Winning should definitely always be a goal so you can try your hardest and tell what works and what doesn't. However, you shouldn't be super worried about losing a lot and having a bad record as it's just going to happen. It's part of improving and a loss is often a lot more helpful than a win.
I think to improve though, sticking with one certain build for a while, until you're at a really good proficiency, is a good thing to do. There are many different builds and many different possibilities, so if you try a bunch of things without extensive you might not know why or if X thing works because your opponent may not have scouted it, or they might have just gone the wrong build, or you might have had better macro, or the map might have been better suited, as well as tons of different things.
Practicing with a solid build for a long time and seeing the ins and outs of the build is IMO better for improvement because your improvement will be more focused.