For all their positives in this compatible combo, on the challenging side we have the stern taskmaster (8) meeting the freedom loving spirit (5). Yes, they can get along but if they dig their heels in with determination to have it their own way - "Houston, we have a problem."
The 8 has the ability to order and demand, while the 5 ignores, lost in the energy they wish to experience. Picking out the other person's limitations and faults, it will point them out at every opportunity if they feel pushed. The 8 will slam it back with "the way it is."
If you find yourself easily slipping into this mode, stop and take a few moments of silence. Begin again. Rarely do we get to where we want to be in a business situation or relationship by demands or bullying, and we'll always remember the ill words spoken.
On the other hand, this can be a great day for taking care of or obtaining new clients and customers. Just remember to treat them as you wish to be treated.