Jonathan Schrantz demonstrates why tactical retreats should be considered. See several notable games involving retreating Knights.
2016.08.23
Alexey Shirov vs Vladimir Akopian, Oakham (1992)
http://www.chessgames.com/perl/chessgame?gid=1123489
David Navara vs Anish Giri, European Team Championship (2013)
http://www.chessgames.com/perl/chessgame?gid=1737340
Aron Nimzowitsch vs Akiba Rubinstein, Dresden (1926)
http://www.chessgames.com/perl/chessgame?gid=1007481