+1 to Tom's comment. You are well aware that it is possible to have a mix sound good on both monitors and headphones. Since you know that, know that is possible for you to get to that point as well. The only thinking keeping you there now is very small changes in your mix. If you made the proper moves in the mix, then you'd have a mix that sounds both good on headphones, laptop speakers, monitors, etc. I know that I'm only stating the obvious, but realize that you're probably not far off, just a few tweaks here and there. So, seriously, just keep tweaking. Listen on monitors, get it right. Then go listen on headphones, and get it right there. Then go to your car, and takes notes on what isn't quite right. Adjust. Different systems will emphasize different frequency ranges of the mix. Personally, I currently mix with monitors which givers me a pretty good picture of the entire frequency spectrum. Then I put on some headphones that are very mid rangey. I make sure that the mids sound good there. They might be too much, they might be to little. I adjust slightly. Then I listen to headphones that accent the lows. I make sure that the bass and kick sound good together there. Soon you'll learn that different monitoring systems will each tell you different things about your mix. As you do this more and more, you'll become more and more familiar with what your system is telling you about your mix and how the song will translate out there. Just hang in there and let your ears become more and more attentive and sensitive to these nuances.