It's quite possible that your general mental state affects your dreams - e.g. if you're feeling stressed then your dreams might well put you in a stressful position. If you're feeling frustrated then you might find your dream puts your feet in treacle, or something else that stops you achieving things etc. I know that when I'm stressed then other than struggling to sleep at all I do find my dreams are more chaotic, whereas normally there's a more defined path my dreams seem to take. At least with regard those aspects I can recall. I also think the having of nightmares itself is an indication of something the subconscious is struggling with. But I also think that many interpretations are a load of hocum: I've heard that to dream of a spider is symbolic of an overly-strong female influence in your life, for example. But then when the "interpreter" is told it's not that they switch it to being something else... and then something else. With regard dream interpretation, I think that the chances that we dream with the same symbolism seems unlikely. Broad situations, yes, I can understand that, and possibly some fairly basic aspects... but when it comes to the interpretation of the finer detail, I think it's just as likely to be unique to the individual, to their own experiences and references, and interpreters are no more accurate than any cold reader might be.
I think I agree with you on this point. I don't believe there is a universal interpretation for dreams, and any attempt to give them meaning must be on a personal level, in reference to one's own experiences. Good point, Sarkus.