Tehillim at Night

Havod Harav, I understand that its best not to say tehillim at night however in our arvit prayer we say some passages of tehillim. Why is tehillim allowed as part of arvit but not allowed if said outside of arvit?

Whatever is in the prayer is not included in the restriction. Obviously those who added those tehilim felt that during the Tfila it doesn’t have negative affect

Rabbi Shay Tahan