Yeah, there's a lot there to learn, too.
My plan to build a custom shelf unit for our kitchen went over-time and over-budget (in the small). Reason: once it was made it became apparent that it lacked strength against skewing deformations, which would not happen ‘laterally’ given where it was sitting but would happen ‘dorsoventrally.’ (Apologies for the anatomical language—it could wiggle side-to-side along its width and who cares because there are walls on either side, but if it wiggles back and forth away from the wall behind it then maybe things start falling off of it or maybe it just collapses some day.)
This sort of problem is of course solved with crossbeams, but like then I had to buy a bunch of wood that was the right width, calculate an approximate length and miter angle for four pieces, of course I did not have the tools to make pocket holes properly (woodworking co-ops closed, thanks COVID) so I just did it roughly (you predrill the screw hole backwards from the flush surface back to the side of the lumber, then you use that hole to guide drilling the pocket) and of course I screwed up one of these four by drilling the pocket too deep because I didn’t have a drill press (thanks again COVID) and so I start low-teching that by just masking-taping the drill bit out to the appropriate depth so that I don't go over. Finally a pair of crossbeams goes in and... it's not symmetric. I think “eh you only see those edge-on so who cares” and install the other beams but the lack of symmetry in installation actually really matters because it means that the crossbeams are pushing the posts off-level, which means the shelves are off-level. Whoops. So this “it is finally ready!” moment turns into a “no it’s not!”
Then, a clever idea: pre-join the cross-beams together at the center of the X (they were not joined initially) before installing them, so they have to be symmetrical. Slight problem: the predrilled holes from attempt #1 in the side beams are now still pulling the crossbars in weird ways and attempting to mess with the level of the shelves. Solution is to just unfasten the X and swap which beam is proximal and which one is distal, then I can pre-drill the holes again, but I'd better just get the thing wood-glued in place first, even without appropriate clamps, so that I am 100% sure it is not going to take the shelves off level when I put those screws in. Finally everything works.
Irrationally undeterred from this success, I am now building a California King bed frame. It is almost exactly 50% complete—there is a facade which is stained but not finished and the center consists of two free-standing “pallets” (not actual pallets, but they look similar) which get bolted together, one pallet is finished and the other is not.
Delays so far have mostly been due to other life circumstances coming up, too much to do on weekends and hot weather baking my garage into unsafe temperatures... but there have already been a few overruns. I realized for example that at the outer corners of the bed frame my screws were going to be taking a heck of a lot of torque (the middle should have two posts side-by-side when the two pallets get bolted together, they can be a little lighter-weight) and revised my design to use some metal corner-ties. But those had a different geometry and so the 2x4s on the sides needed to be cut even shorter. Then I realized that I had calculated this ad-hoc cut assuming that it needed to be shorter by a 2x4's width on both sides but I had forgotten that I wasn't doing the same corner ties for the middle posts of the bed that get bolted together, so I bought a new 2x4 and while I was there I bought some tie plates to try to strengthen those middle posts a little more anyways. So we've only overrun the initial cost by 4 tie corners and 4 tie plates and one 2x4 which is not so bad, but still.
I do not recommend doing your own woodworking in order to save on cost, it costs a lot of time. I do recommend it if you feel like carpentry connects you to Jesus or if you have a really specific idea about what you want in a space and nobody anywhere seems to be offering that exact thing.