Dropping out of the throw-away society.
A few months ago the straps on my backpack had broken. My sustainability action today was to take a needle and thread, then repair those straps. I am useless at sewing. My handiwork won no prizes, but those straps are now sewn in, my backpack is reusable again.
If an item can be repaired so that it safely can continue to serve a useful purpose, this is good sustainable action. Being part of a throw-away society that throws away repairable items is unsustainable.
I have some socks with holes in, so I will be getting some further opportunities to improve my sewing skills soon.