JFK once said:

"One person can make a difference, and everyone should try".

i.e. Don't leave it to others. One current example of this is the growing problem in Syria. We should all contact our MPs, lobbying them to make sure they make the right decision (whatever your point of view). If we leave it to others, we can't really complain if they carry out policies we don't like. The Conservative party may well have a majority in the House of Commons, but that majority is small enough for ordinary people like you and me to make a difference, whether our politics is to the left or the right. Nowhere near enough of us take the trouble to vote at the General Election (maybe we should move towards mandatory voting as in Australia?) and even less of us bother to contact our local Member of Parliament to put forward our views.