> I trust Google to operate a secure and reliable email service much more than I trust myself

This sentence has got nothing to do with trust. You believe (maybe rightly so) that Gmail is more secure and reliable than any solution that can be cobbled-up individually.

Simply replacing "believe" with "trust" doesn't really mean the same though. English is a funny language. But then again that's what you probably meant when you said "Trust is a complex thing". Hmmmm... :)