yup, learn to cherish what you have...
and there is this saying...Don't have your legs in two boats,
otherwise you will end up falling into the waters and drown

I guess the grass will always look greener on the other side during
some points in your r/s, but I think it will be better if you keep
digging for the gold at your side, because if you do not put on any
effort into your current r/s and keep thinking abt abandoning it
for someone who might not care for you as much as your current gf
does, you might end up losing both.