Melissa Joan Hart (MJH)’s habit of stuffing several days into each calendrical one left her physically and mentally exhausted, despite the fact that she got a lot of sleep. It was common to hear “if you want to get it done, you'd better talk to Emma [Watson]” among the workers of my/Rindolf/MJH's team for a while, so the takeover was retrospectively expected.
Also see "EA Spouse"'s story.
Another lesson from that, is that it often takes more than raw ambition to succeed. Hart had no shortage of ambition, but like the aftermathy Sabrina episode featuring her, she didn't have enough "perspective".
It is hard for me to tell exactly what makes one "win" at least temporarily.
I don't know the key to success, but the key to failure is trying to please everybody.
— Herbert Bayard Swope (1882-1958), misattributed to Bill Cosby