The 18-year-old has already scored four goals in seven appearances in all competitions this season, forcing his way into Mourinho's first-team plans despite the signing of prolific striker Zlatan Ibrahimovic.
"A lot of things happened last season and it is now behind me. It was last season," Rashford told the club's website (www.manutd.com).
"I have to try and recreate those moments this year and to get the goal early in the season was quite important for me to get back on a roll. I am just looking to build momentum now."
Rashford also described last month's 92nd-minute winner against Hull City in his first league outing under new manager Mourinho as his most important goal for United since he was handed his debut under previous coach Louis van Gaal.
"It was a different moment for me and I don't think I've scored one so late in the game before. It was an amazing feeling to be with the travelling fans as well, a brilliant feeling," Rashford added.
"I feel like that was the most important goal for me, to get the winner in the last minute away from home. I like the feeling that it gave me and I want more."
United, who are sixth in the league standings, host struggling Stoke City on Sunday.
(Reporting by Ian Rodricks in Bengaluru; Editing by John O'Brien)
