Here's a good example of why short-term price fluctuations don't matter at all to me.

$JUN3 (-1,04 %) vs. $VIB3 (+0,33 %)

Jungheinrich are today temporarily +12% up. Villeroy&Boch, on the other hand, slumped -7.5%. Look at my portfolio, in the long term this does not bother me at all. Of course, everything should generally be in order with your investments. Otherwise, do not panic 🙃