Mourners gather at 9/11 Memorial, united in pain and sorrow

LOWER MANHATTAN, Manhattan (WPVI) -- They come from all walks of life, and from all corners of the world. For some, this is a painful journey.[br /][br /]Maria Zeitlin lost loved ones - firefighters with Ladder Company 3.[br /][Ads /][br /]"Fifteen years later - it's yesterday, but it's also a million years ago. And my heart's bleeding. It will always bleed," Zeitlin says.[br /][br /][twitter ID="774763603882893312" /][br /][br /]Others are so young, that September 11th is not even a memory for them - so young that they can't even begin to understand what it did to us.[br /][br /]"It's difficult. It's a difficult conversation to have, but you know, it's a good one to have, and that's certainly why we're here today," says Sean Latimer.[br /][br /]What unites all of the different people who visit the 9/11 Memorial is the pain that still pierces our hearts, and the sorrow that comes with that day 15 years ago that changed our lives forever.[br /][Ads /][br /]To honor those who rushed into danger when others ran the other way, a solemn memorial service was held at St. Patrick's Cathedral.[br /][facebook URL="[br /]https://www.facebook.com/FDNY/videos/vb.304603755728/10154404444205729/" /][br /][br /]343 firefighters died in the September 11th terrorist attacks. Firefighters who carried the wounded on their backs, and carried a city and a nation when we had trouble standing.[br /][br /]"The horror, the sense that we were dealing with something that we have never seen before, and we relive it this time of year - it comes back in waves," said Mayor Bill de Blasio.[br /][br /]The courage and the honor of those fallen heroes are found in the daughters of Battalion Chief Joseph Grislack - living reminders of the burden we bear, and the hope that gives us the strength to move foreward.[br /][br /]With Sunday being such an important day, there were so many who Eyewitness News spoke to who said they came Saturday to not only try to get a little more of a private moment, but also give those families on Sunday a little more time to grieve.