Wondering Where the Limit Line is

How do you know when you can actually trust someone? Can you just keep up with the excuses to questions you ask? Can you overlook the "little" things? The flirting? The double standards? The things you discover? Sure there are reasons to it all, but when is too much, too much? How can you trust someone after so many things keep turning up? Shouldn't there be communication in a relationship? Aren't you supposed to be able to share everything with the one you love? Doesn't it make more sense to share it in the start and face what could happen then to let it appear down the road and have someone hurt by it? How much can you love someone till it all becomes too much to keep holding onto?