What are you using on your mattress to sleep in/under?
Usually ventilation is the key to reducing condensation.
Is the condensation forming on top or underneath the mattress? If it is underneath (between the floor and the mattress) then using something to insulate under the mattress, like a picnic rug, may help.
We used one of these for 12 months before getting the camper trailer and we may have had a slight dampness on cold mornings but nothing that needed mopping. Do you get condensation on the walls/roof of the tent - if so increasing the ventilation is probably the way to go.
The alternative is to breath less!