Yes to painting or varnishing furniture.
I'm such a bloody perfectionist, that shabby chic upcycling is NOT on the agenda.
Constant rounds of sanding, washing, letting dry, gently coating with thinned varnish or paint, letting it dry, feeling for roughness, cursing my luck for finding a rough patch, sanding again, washing again, letting it dry again, gently brushing with thinned varnish or paint, letting it dry and so on.
One chair can take fucking weeks.
Starting any DIY project.
The latest was putting up an IKEA magnetic bar onto a wall for with magnets for sorting paperwork.
I found it in a charity shop for £1.49, but the screws and rawlplugs were missing. That's OK, I've got plenty.
Trying to put three evenly spaced, level holes into a wall, banging in three rawlplugs and screwing the bar to the wall was NOT the ten minute job I thought it was going to be.
It took faaaaar too long for me to realise that the drill was set to go backwards. 
Starting any cross stitch project with a recipient in mind.
It's always more complicated and tedious than I realised. I just see patterns that I like and fail to look at the pattern too closely.
The last gift contained variegated threads, blended threads, fractional stitches AND French knots.
That's before I lose count, unpick a good third of the canvas and have to pay for more thread as the kit doesn't have enough to cover my mistakes.