To fix a sagging latex mattress, you should inspect the mattress for any broken or curled wire supports. If there are any areas of the mattress where the wire has broken or curled around itself, it should be repaired or replaced. Additionally, if the mattress is held up by a box spring or bed frame, make sure that it is properly supported and leveled. If necessary, add extra slats beneath the mattress to offer extra support, or get yourself a firmer latex topper to improve support. Finally, rotate your mattress every six months to prevent long-term sagging.