You just said it: time. It's completely normal to experience grief over something or someone we grew to value when it's disrupted. I terminated regular therapy sessions with a T I liked very much last November and it was quite uneasy for a couple weeks, I literally had cravings for the connection. Most likely it'll get gradually less frustrating over time and perhaps it'll transform into positive memories and appreciation. Just allow yourself to experience the feelings as they surface and view them without reacting if possible.