With the completion of the tour, Cotter said they could have done much better.
The Flying Fijians won their first game 43-13 against Spain, lost to Wales 23-38, and were held 15-all by Georgia.
Cotter said the key theme coming out of the Wales match was discipline.
Winger Eroni Sau was suspended for five weeks following his red card for a dangerous tackle in the game, but Fiji also picked up two yellow cards in Cardiff.
Cotter says the squad has to get its attitude and mindset sorted out, and follow a good game with another top-notch performance.