Just when I started typing this post the parallel of what it talks about and life in general came to mind. Underneath part of the floor (the bathroom in particular) someone else proceeded to hack away the support to make space for some piping. They basically took the support and cut it in half, leaving what was left hanging there to hold the weight of the house above unsupported. So I had to get a jack post and push back up the sagging joist into the correct position. This was done over a couple weeks, in small increments, just to make sure I didn't stress everything all at once. After it was in the correct position, I installed a new double header spanning from the joists on each side, then attached the cut joist. I used some joist hangers to make sure there was a secure connection between everything. I don't have any pictures of the hack job, I forgot to take one before tearing the old stuff out. But you can see in the images how the new header fits in, the support post has been removed and now the floor isn't sagging!
If only it was this easy to fix life after it's been cut in half, it takes quite a bit more time and effort, but you definitely need good support during that time to get things back somewhere close to level.