Orient face the Gunners in Wednesday's FA Cup fifth-round replay at the Emirates Stadium.
Midfielder Smith joined Chelsea aged nine and went on to spend 13 years at the club before he was shown the door in 2009 after realising that he was fighting a losing battle to beat the likes of Frank Lampard and Michael Essien to a first-team place..
The 24-year-old went on loan to QPR, Norwich, Sheffield Wednesday and Orient before signing a permanent deal at Brisbane Road in the summer of 2009.
He left the Blues with just nine minutes of game time to show for his time there, as a late substitute against Newcastle.
He admits losing out on the dream of playing for the Premier League champions hurt, and is determined to prove his former employers that they made a mistake by continuing his recent good scoring form against the Gunners on Wednesday night.
"Leaving Chelsea was heart-breaking," he said.
"I was there for a long time but I looked at myself at the time and I felt like I needed to move on and think about myself. I wanted to be playing every week. I didn't just want to be a number. That's why I decided to leave.
"Moving has made me a better person and footballer. I feel like I needed to take a step back and hopefully I will end up taking two steps forward. I know I can.
"The Arsenal match is a chance for me to show that I can cut it at the top level. Everyone wants to prove themselves to a lot of people and I'm no different.
"I'll be playing against Arsenal, who are one of the best teams in the world, and I want to go out there and do the best I can."
The move seems to have worked wonders for Smith, who is now keen to add to the eight goals he has scored so far this term and set up another money-spinning clash against Manchester United in the quarter-finals.
"It would be amazing to score at the Emirates," he said.
"Not just for me, but for the team, because we know that the prize if we win the will be to play Manchester United away."
Around 9,000 Orient fans will make the short trip to the Emirates after the shock 1-1 draw against the Gunners at Brisbane Road last month.
The O's are expected to rake in around £1.5million from their cup run and Smith admits the club has been gripped with excitement ever since Jonathan Tehoue grabbed a late equaliser against Arsene Wenger's side nine days ago.
"It's going to be amazing. When we knew we had the draw, the queue of people that went around the stadium went on for miles," he said.
"I have had a few people that have texted me asking for tickets and I don't even know them. I'm trying to get everyone there that wants to go but it's hard."
Wenger has called on his side to bounce back in style from their Carling Cup final defeat to Birmingham on Sunday, but Smith hopes the defeat - which came courtesy of a terrible mix-up between Laurent Koscielny and Wojciech Szczesny - will have dented the opposition's spirits.
"Hopefully it will have knocked their confidence, but we all know that there will be 11 internationals out there for them and it will be a great test for us," he said.
"Everyone thought that they were going to win the cup but the underdogs won so hopefully it will be the same on Wednesday."