Which is more stable? CF2 (singlet) or CF2 (triplet) Generally, we know that triplet carbene is more stable than singlet. But in my book, it is written that singlet difluorocarbene is more stable than triplet difluorocarbene.
What's the reason for it?
So generally singlet is less stable as triplet has half-filled orbitals which leads to stability.

However whenever a group that can give  electrons by back donation (examples being lone pair carriers like $\ce{-OH},$ $\ce{-NH2},$ etc. are attached, they stabilise the singlet by back donation of their lone pair into the vacant orbital of the singlet carbene.

This is similar to back bonding in $\ce{BF3}.$