Palestinian political leaders seemed to be listening. Within weeks, somewhat out of the blue, a reconciliation deal was announced.
Orchestrated by the new leadership in Egypt, it was meant to end four years of bitter and sometimes violent division between the two main Palestinian factions.
Three months on, Abu Yassin is angry: "Nothing has changed.
"We're really disappointed. This deal was just signatures on paper. We wanted real change on the ground."
Abu Yassin is right. On the ground, there is little difference. The Islamist movement Hamas remains in power in Gaza. Its secular rival Fatah runs the West Bank.
Wrangling
No power has been shared. The security forces of the two factions are not working together. And crucially there is no shared policy on key issues such as relations with Israel.
Under the May reconciliation deal, the two sides agreed to establish an interim government made up of independent political figures. The government would have no Hamas or Fatah members but would work towards preparing for long overdue elections later next year.
Three months on, no interim government has been formed.
When Hamas and Fatah first presented their lists of recommended candidates for dozens of ministerial posts, they could not agree on a single name, let alone a whole cabinet. It did not bode well.
The most high-profile dispute has been whom to appoint as prime minister in the new interim government.
President Mahmoud Abbas - who leads the Fatah party in power on the West Bank - wants Salam Fayyad to stay on in the job. Mr Fayyad, a US-educated former IMF official, is an independent.
Hamas does not want him. It says he has too many ties to the West and has compromised too much.
Bad blood
Some, though, feel the bickering over ministers is just an excuse for the deal not to happen.
"The division between Hamas and Fatah is not about the prime minister or who gets how many cabinet seats here and there," says Omar Shaban, a political analyst and economist with the Gaza-based think-tank, Palthink.
"It's much deeper than that. It is about their ideology, their agendas, the history, the desire for revenge between the two. Political unity is an illusion."
The divide between Hamas and Fatah has sometimes been bloody and violent. Hundreds of people were killed in fierce fighting between the two factions in 2007 when Hamas forced Fatah from the Gaza Strip.
Hamas believed Fatah was trying to carry out a coup after the Islamist movement won parliamentary elections in 2006.
The violence has left deep running scars through Palestinian society.
"It's hard to forgive. Even the Koran gives me the right to retaliate," says Ashraf al-Rass as he shows me photos of his brother Salem, a Fatah fighter.
Hamas gunmen shot and killed him in a gun battle in 2007.
Mr Rass says he hopes political unity can be reached but the look in his eyes suggests he is not hopeful.
His mother Umm Harbi al-Rass fights back tears as she points out a picture of Salem, her eldest son, shortly before his wedding day.
Lives were lost on both sides.
"I wish my son had died a martyr fighting the Israelis, not in this stupid fight," says Ibrahem Nassar at his money changing shop in Gaza City.
His son, Abdera Rahman, used to be a bodyguard for Hamas Prime Minister Ismail Haniya.
Fatah fighters killed him when they ambushed Mr Haniya's convoy in southern Gaza in 2007.
Mr Nassar, an elderly man with a thick beard is from one of the biggest Hamas families in Gaza. As he pours me an orange juice, he says he is willing to forgive, but only if the other side does the same.
Foot-dragging
There seems to be a mutual mistrust.
I put this point to Mustafa Barghouti, an independent politician who helped negotiate the May reconciliation deal.
"Unity is not an illusion," says Mr Barghouti, who many tipped to get a place in the new interim government.
"A lot of things have changed. Three months ago, Fatah and Hamas were fighting. They were attacking each other on a daily basis. Today we have something like a complete ceasefire. That's better than what we had three months ago, but it is not good enough."
Mr Barghouti says he believes the US and Israel are trying to undermine the deal. He points to the US threat to cut off millions of dollars worth of funding to President Abbas's Palestinian Authority if Hamas enters a government.
But Mr Barghouti admits that personal political fiefdoms are leading some to drag their feet: "There are certain people in the bureaucracy of Fatah and Hamas who feel they will lose positions because of this reconciliation agreement and these guys are not enthusiastic to make the deal work."
Other analysts believe both Hamas and Fatah have now got cold feet.
"Both sides are waiting," says Mokhaimer Abu Sada, professor of politics at al-Azhar University in Gaza.
'Wake up'
"President Abbas is waiting until after September because he doesn't want to jeopardise his United Nations plan. Hamas is waiting to see how the Arab Spring plays out. To see what happens in Egypt and Syria."
President Abbas says he is planning to go to the UN next month to try and get Palestine accepted as a full member state based on the pre-1967 borders, a move senior Hamas leader Mahmoud Zahar calls "just nonsense."
Mr Abu Sada believes President Abbas is fearful that if he is seen to be getting closer to Hamas, an organisation the US and the EU regard as terrorists, it could scupper his chances at the UN
But Abu Yassin, the young unity demonstrator in Gaza, says Palestinians will not wait forever for reconciliation to become a reality.
"Our patience is not going to last for long," he says.
"We're going to take to the streets again and again until we see concrete steps that show there is reconciliation."
And Mustafa Barghouti agrees.
He says some in Hamas and Fatah signed the deal because they were worried about public opinion when much of the rest of the Arab world was rising up. He says they need to wake up.
"This unity deal started on the street," Mr Barghouti adds. "Some people in Hamas and Fatah signed this deal thinking they would never have to implement it. This will go back to the street if things don't change."
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