Can I ask, did someone die when you were a kid? It's just that you mentioned the coffin/clock/piano thing which can all kind of be connected with death - coffins obviously; pianos also have lids that close down with a finality like coffin lids, and they are made from similar materials of similar colours; and the clock obviously suggests the passage of time and finite existence... Coupled with the fear of mirrors, which seems like an anxiety/low self-esteem thing which could be brought about by something drastically and unexpectedly changing like a mother/father/sibling dying - they're all very deep thinks for a young child to be dreaming and thinking about if this isn't the case. Your mind will often try and achieve, often succeeding, the impossible during sleep; you have to look at the kinds of things you try to do and see if you can relate them to your waking life. Like you said, none of the things you dream about mean you are insane; it's just different ways of trying to resolve emotions and thoughts in your mind.

You could check out the Dream Themes page, especially the 'children's dreams', 'dream archetypes', and perhaps 'anxiety dreams' and 'color and dreams'. I realise you're not a child now, but if you can find out why you were having those dreams and thoughts in the first place, it might help you now.