The Beis HaLevi states that the mitzvah of Ahavas Yisrael can be fulfilled by harboring love for every fellow Jew within our hearts, which indicates that this mitzvah can be performed constantly, regardless of one’s location. 

Expounding upon this concept, Sefer Yesod V’Shoresh HaAvodah (1:7) suggests that even in impure environments, where prayer or study is unfeasible, one can fulfill this mitzvah through contemplation alone, by filling his mind with thoughts of love for a fellow Jew.