Sight-reading gets easier the way everything does: badly, then a little less badly, for a long time.

Improvement has a shape, and it is not a flattering one. You are bad, then slightly less bad, and that second stage lasts far longer than anyone expects, with no single moment where you become good. Expecting a breakthrough makes the normal slow version feel like failure. Accepting the shape is what lets you stay long enough for it to work.

Give the thing you are learning a fixed stretch, say eight weeks, and agree not to judge it before then. Keep sessions short and frequent rather than long and rare. At the end, compare yourself with week one instead of with the person you admire.