Spurs topped their Champions League group after a 3-3 thriller with FC Twente.
Defoe, who marked his first Champions League start with a double, said on Sky Sports: "We worked so hard to get here and you have to make the most of it.
"We've scored a lot of goals but it's also important not to concede too many so it was frustrating tonight.
"We'll take each game as it comes but we're playing well and scoring goals and there are one of two injuries to come back in too.
"We're looking good at the moment."