Ask HN: Teach me something new
One of the most deceptively dangerous projects that a DIYer can take on is bathroom wall tiling re-grouting.   Tiles may not have a strong bond to their substrate and once you remove the grout may fall into the tub/floor, usually breaking.  Then, when you search for tile replacements you find no perfect match for your old tile.  Always put a heavily padded rug or blankets over the tub before doing tile work so that fallen tile do not break.  Also, if you re-tile, buy a lot of extras and keep them stored safely.  Oscillating multi-tools are the best for removing old grout, but their vibrations will shake the wall, loosing tiles that you've removed grout from.