Your stats are a very, very rough representation of your performance. There are a lot of situations where the "correct" play and the play that is best for your stats are very different, the obvious example is running onto the point during overtime on KOTH, another example I like a lot is prefiring hiding spots as scout.
But its not like they mean nothing, if youre going 7:24 on pocket in a tf2center there's probably a bunch that can be improved, but you shouldn't look at it like "I need to improve, I went 7:24," but instead like "I need to improve, I often find myself caught out in post-ubers" (arbitrary example).
Also, it's just a lobby and sometimes games are outside of your control. Don't stress too much over individual games it's bad for your mental.