emotional burden

I don't think we're getting enough context here to really be of help, Antonia, but yes-- I think emotional burden is a good phrase.  A wayward child is an emotional burden to its parents.  We can carry the emotional burden of a difficult or failed relationship, especially of our own shortcomings in it.  I suppose that we all accumulate an emotional burden throughout our lives-- an accretion of losses and failures of all types.  However, I cannot imagine this burden being divided within ourselves; it could of course be shared by others, either with the affected partner or, in another way, with a priest.

Well, I cannot see that a mistress would be a burden-- more like a delight.  Otherwise, your idea seems OK.  Let me suggest some corrections and amendations for you:

Those who incorporate the mistress into their routine in advance are better off than those who have not prepared themselves, and who thus shake feverishly like little boys.  It is even easier for those who have several mistresses at once, and thus divide the emotional burden into smaller portions.