Admittedly, politics is not my strong point and I have been studiously avoiding any news about Brexit because nothing is more guarenteed to ruin my day than hearing Leavers try to justify what they did, however, my understanding is...
May (unelected) and her cabinet (unelected) wanted to trigger Article 50 on their terms. AFIAK they were going for a 'hard' brexit. No-one voted for a hard brexit, there is nothing to say that the majority of Leavers want a hard brexit, we weren't given any option to vote on how we wanted to leave.
This ruling means that May now has to debate Article 50 and the terms of leaving with our elected parliament, who now get to push for what they and their constiuants want from brexit.
Did you want bendy bananas and burnt roasties but also wanted to keep workers rights and the freedom of movement for workers? Awesome, write to your MP and ask him/her to push for a brexit that will allow this.
There is very little chance that your MP will vote against brexit if your constiunacy voted for it, but they will get a chance to have their say over how we leave.
Taking the power away from May to do whatever she wants is no bad thing. That is not and should not be how our democracy works.
I'm happy to be corrected if I am wrong, but that is my limited understanding of what this ruling means.