  Electronic nematic behavior has been identified and studied in iron-based
superconductors for some time, particularly in the well-known BaFe$_2$As$_2$
system, where it is well-known to compete with superconductivity. On the other
hand, it has been shown recently that FeSe displays a negligible effect of
nematicity on superconductivity near the superconducting transition, and actual
cooperation between the two orders when the system is doped with S. Recently it
has also been proposed that LiFeAs undergoes a nematic transition in the
superconducting state itself. Generally, we expect superconductivity to be
anisotropic when it coexists with nematic order, but it is not clear under what
circumstances the two orders compete or cooperate, nor how the anisotropy of
the superconducting state correlates with that in the nematic state. To address
this, we study a simple mean field model of a $d$-wave Pomeranchuk instability
together with a mixed $s,d$ pairing interaction, and identify when nematicity
is enhanced or suppressed by superconductivity. We show that the competition or
cooperation depends significantly on the distortion of the Fermi surface due to
nematicity relative to the anisotropy of the superconducting gap function.
Further, we discuss the implications of our results for FeSe and LiFeAs.
