I think it means if you're overambitious you'll never be truly happy with what you achieve, no matter what. You'll always want more so even when you suceed there will be a bitter taste to it.
^ that's good.
mine take is pretty much the same. even if you are successful, if you are also an ambitious person, you will always be trying, biting your nails in anticipation or stress, for whatever's next, because you are always looking for progress, even when you have something good