The above posts are true; you have to learn your equipment and not trust one source when mixing.
Play the resulting mix everywhere you can (phone, car, home theater, studio monitors etc) and then judge.
But also learn what your original mixing source 'caused'.
This is part of the 'Learn To Trust Your Ears' concept;

If your headphones produce too much bass, and thus you lower the bass in the mix, but then it sounds tinny everywhere else .. well you learned something.
Your headphones are bass heavy.

Once you learn this you can either;
1. compensate moving forward
2. get headphones that don't produce too much bass

Once this is solved, learning how to 'hear' the image in the headphones as far as stereo becomes a much more solvable task.
Simple example: import your end result stereo wav file into RB to two separate mono channels .. and pan them to less of a 100% R/L mix. In RB you would (for instance) set the panning for the L/R to 60 and -60 to bring the image (perceived appearance of the stereo field) a little more narrow.

Just because you use headphones doesn't mean you can't test your mix in differing 'live' scenarios, or at least approximate it.
But even then, go listen in the car, living room, phone .. anywhere a real person may listen. You can't cover every possible scenario (there is no 'BrowserStack for Audio' where you can test on multiple devices at will) but we can try by testing with everything we have. <grin>

I do not work here, but the benefits are still awesome
Make your sound your own!