The donkey is read as patient labour and quiet stubbornness. In folk tradition it carries the loads others will not, so it often points to a burden you have taken on without complaint.
When this appeared in your dream, what were you feeling?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.