The highly-rated youngster has made four appearances for the senior team after a series of excellent displays at youth level caught the eye of Arsène Wenger.
"It's the biggest confidence boost you can have," Gnabry told Arsenal Player. "Arsène Wenger is one of the greatest coaches in the world and I'm happy to be in that position. I try to give him back what he believes in me.
"Since the start of pre-season, it's gone very well for me. I've played in the Premier League and the Champions League, and of course that's a big step. I'm very proud. I always thought that in football it can go quick or slow, but I didn't expect it to happen so quick.
"It's the mental side that's hard. But you get used to it. At the beginning it's a bit different - the stadium [and] the crowd. It's lovely to be there. There's bigger people who are very powerful. It's kind of new, because I played against my age group before and now to play against 30-year-old men is a bit different."