This is the 113th most frequent Serbian word.
због
"Због" means "because of" in English.
'Због' is used here to introduce the cause or reason for not going to the park, which is the rain.
Због кише нисмо могли да идемо у парк.
Because of the rain, we couldn't go to the park.
'Због' in this sentence introduces the reason for his sadness, which is associated with the breakup.
Био је тужан због раскида.
He was sad because of the breakup.
'Због' here specifies the reason or influence that led to learning to trust people, which is attributed to 'you'.