Sometimes it is really difficult telling who your real friends are. Especially when people give you negative advice under the guise of imparting such wisdom 'for your own good.'
People can also get upset when you question their motives. Yet, it is necessary, even if you only ask the question inwardly, to wonder why people are telling you such things.
Sometimes it is easier not to share your ambitions with others. People will more often than not trample on your dreams. This will happen when people are not happy with their own circumstances but are too cowardly to do anything themselves. You are therefore insulting them when you express such desires etc.
Geoff Thompson in his book 'Shape Shifter' discusses this and talks about the lobster effect. When fishermen lift into their boats the lobster pots, the lobster at the top could have always easily escaped- if only the lobster below had let it go! Human beings can work in just the same way.
This is not to say that all human beings are alike. There are good friends out there who will support you. There is a time and a place however to share your dreams and aspirations. Choose your friends carefully.