What is the relationship between fear and desire? Are fear and desire located on the opposite sides of a spectrum or are they more like filters/lenses through which one can look simultaneously?
The Atlas of personality, emotion and behaviour (Mobbs, 2020) is able to visualise emotions in two dimensions: affiliation and dominance.  Fear is considered submissive and disaffiliative.  Desire is more dominant and intrapersonal, that is, in itself neither affiliative or disaffiliative.

Reference
Mobbs AED (2020) An atlas of personality, emotion and behaviour. PLOS ONE 15(1): e0227877. https://doi.org/10.1371/journal.pone.0227877
Declared interest
I am the author of the atlas paper.