The 28-year-old forward could have become an unrestricted free agent after this season, which will be the final season of a six-year contract he signed Nov. 29, 2014.
"It was hard, if I'm being honest. It was tough," Gallagher said. "It was really the first time since I've been a Montreal Canadien where that thought went through my head that I was going have to make decisions coming up in my future, whether I wanted to remain a Montreal Canadien, which was hard for me. It's the only team I've ever known.
"You really fall in love with everything about it and I don't do well with change, so it wasn't something I was all that happy about and all that excited about. It might have felt like a pretty short turnaround for everyone else but for me it felt like an eternity. It was obviously nice to wake up the next day and, you know, have a little bit more positive news."
Gallagher scored 43 points (22 goals, 21 assists) in 59 games with the Canadiens last season and tied Tomas Tatar for the Montreal lead in goals. He scored four points (one goal, three assists) in nine postseason games. The Canadiens defeated the Pittsburgh Penguins in four games in the best-of-5 Stanley Cup Qualifiers before they were defeated in six games by the Philadelphia Flyers in the Eastern Conference First Round.
"I'm just there to do my job," Gallagher said. "I think my role in the organization has grown and changed since I first became a member of the Montreal Canadiens, but you know my job doesn't change. I'm there to work, and when you're at the rink that's what you're there to do. And I've been pretty fortunate. I've had great teammates and coaches, and obviously the GM (Marc Bergevin) and the owner (Geoff Molson) have put lot of trust in me as well. It's been pretty easy."
The Canadiens this offseason have added forward Tyler Toffoli as a free agent (four years, $4.25 million per season) and traded for forward Josh Anderson and goalie Jake Allen. Anderson (seven years, $5.5 million per season) and Allen (two-year extension, $2.8 million per season) each then signed a new contract.
"Honestly, it's unbelievable to see the additions we've been able to make," Gallagher said. "… Every one of them is going to play a key role on our team, and to be able to have that many pieces is pretty exciting, so when I'm sitting there thinking about where you want to be, you add those pieces on top of what we had as a group and what we were building. You talk about the young talent coming up, it's pretty exciting right now for anyone around the Montreal Canadiens organization."
Bergevin believes the addition of Toffoli and Anderson will relieve some of the scoring pressure off Gallagher.
"You know Gally's track record of scoring goals -- 30 back to back (31 in 2017-18, 33 in 2018-19), and he probably would have had 30 this season," Bergevin said. "With Gally scoring 30 goals, we still didn't make the playoffs, so hopefully with the people we're bringing in, he might score less. It doesn't mean he's less effective, doesn't mean he's not doing his job. It's just that there's more scoring to go around and that hopefully translates to team success. Gally might get less but it doesn't mean he's slowing down. It means that somebody else is scoring too."
Selected by Montreal in the fifth round (No. 147) of the 2010 NHL Draft, Gallagher has scored 334 points (173 goals, 161 assists) in 547 regular-season games, including scoring at least 20 goals four times in the past six seasons. Gallagher has scored 25 points (11 goals, 14 assists) in 49 Stanley Cup Playoff games.
NHL.com columnist Dave Stubbs contributed to this report