A weekend does not require a bigger bag. It requires deciding, before you pack anything, what the bag has to do on the walk between the station and the door.
Pack in layers, not piles
Load the heavy things first and keep them against your spine. A laptop, a charger brick, a pair of shoes: these want to sit high and close, where they pull straight down rather than swinging away from you. Clothing goes around them, filling gaps instead of forming its own stack.
Two days is four outfits, not six
One on your body, one for the evening, one spare, and something to sleep in. Everything past that is optimism. Roll rather than fold, and put the roll you will need first nearest the opening.
Keep the small things findable
Cables, keys, transit card and charger belong in one pouch that never changes position. The point is not tidiness for its own sake. It is that you can find a charger on a moving train without unpacking the bag onto your knees.
Leave room to close it properly
A 24L pack that is stuffed to the seams carries worse than a 20L packed with intent. If the top compresses flat and the panel still sits against your back, you have packed it right.