One good way to help a sim at work to stay if not in the ideal mood then at least happy, is to have another sim write a Book of Life and then capture the working sims Epic Saga. While at work have your at home sim read the working sim's Book of Life... this will top up the working sim's needs just like a moodlet solver. The benefit being that the working sim can now have full needs the entire time they are at work.
Also if the working sim should become stressed from working hard, the at home sim can read the Book of Life and this reduces the time of the stress moodlet. Keep reading the working sims Book of Life until the stress moodlet goes away. Usually takes about 3 readings.
The at home sim could actually be at the park or any other lot, as long as they have the working sim's Book of Life in their inventory they can read it wherever they are.
Of course, you need to have a sim complete the Best Selling Author aspiration to be able to write a Book of Life but if you dedicate a few days to this it isn't that difficult to complete.
One of the best ways to keep a sim in the ideal mood for the entire working day is to use the cow plant. Get a sim in the mood you need, say focused. Feed them to the cow plant once, then milk the cow plant. This will give you a focused drink which, when drunk, will give a sim a 12 hour moodlet. If you have the cloning machine, you can clone and endless supply of these cow plant essences. Easy to drink, takes one sip... and your sim is ready for work in an instant.
If you don't have the cloning machine then you will need to use either a moodlet solver on the 'eaten' sim or take multiple baths using the most expensive bath until the 'drained' moodlet has gone. If you feed a sim to the cow plant with a 'drained' moodlet they will be eaten again and die. Once the 'drained' moodlet has gone, get your sacrificial sim into the correct mood you want... and feed them to the cow plant all over again.
Using these techniques and a few other tricks I regularly max a career in about 20 sim days. So my sims can max a career during their young adulthood leaving them to do something else when they become an adult.