Being abandoned in a dream is a complex symbol which may mean that it is high time you got rid of old worries and problems, solve them and move on with your life or that you have recently suffered a loss which you haven't recovered from yet.
However, the simplest interpretation of abandonment as dream image relates to your inner fear of being left alone, in isolation, of not receiving enough affection from friends and family etc. You think that people you care about will neglect or desert you sooner or later and you won't be able to live like this. You should learn to put more trust in yourself and your own qualities. You should also grow aware of the fact that it all depends on you when it comes to keeping friends and dear persons close to you.
If you see in your dream a situation in which you are abandoned by others, this may also mean that you have not reached a balance in your life yet, though you are striving hard to put things in the right order. Being abandoned may also closely relate to a feeling of self-unworthiness and a general low opinion on the self.
Being abandoned in your dream may also be caused by unsolved childhood issues which still give you a feeling of insecurity or make you feel unprotected and not loved. The feelings of not being worthy of love and affection may also derive from a present relationship in which you do not feel comfortable or secure.
For instance, having a dream in which you are abandoned by your lover for a more beautiful, influent, or stronger person, is rather easy to be interpreted: you are afraid that your partner does not love you as much as you love him/her, while the person your lover leaves you for is the embodiment of all physical and moral qualities you wish you had, but you don't.
Another possible interpretation of a being-abandoned dream is that you are very attached to, even obsessed with, someone in your waking life. In this case, you should learn to let go and avoid fully depending on someone.
On the other hand, if you abandon other person(s) in your dream, it means that you are suffocated or overwhelmed by problems or difficult situations in your real life. Also, abandoning someone means that you are annoyed by something/ someone and you feel the urge to remove this burden from your life.
Abandonment coming from you in dreams may also be closely connected to a feeling of guilt which haunts you after you have neglected or disappointed someone in your real life. You have remorses and you wish you were there for that person when he needed you.