This article takes on this subject from an angle that I've never really considered before (well, I actually wrote the article in question, but before I wrote THAT I hadn't considered it!) Usually when you ponder extra workload and demanding bosses, you believe it to have a negative connotation, but actually, this could be happening for a far more positive reason than you might think.
In some instances, if the boss is giving you extra work and involving you in cross-functional projects, it kind of means that:
A: They like you
B: They trust you
C: You're good at your job
Of course there could be many situations where this may not be the case. For example, if you work for a small company, how do you really know that the extra workload is in your best interests or if it's just abuse of your time and (possibly cheaper) labour?
Have a read:
Take it as a compliment! We know how difficult it can be to feel snowed under. The pressure of a continual barrage of work with seemingly no end in sight can be daunting. You may find yourself feeling unable to cope and wondering why you're being 'punished' with an abundance of new tasks, but perhaps there's no need for negativity after all! If your boss is giving you more work to do and involving you in 'extra curricular' projects, this can actually be a huge compliment and a testament to the work you do.