I don't keep anything on my phone or on the internet unless I'm okay with it being in the public domain. Anything more private than that, you'd have to ask the NSA for. I'm sure they could tell you everything about me.
That, and I use an old Motorola Razr V3 from 2005. If you wanted to have a look at my contacts, or my latest text message from my parents, you could come up to me and grab my phone and have a look if you want. I'm not saying I'm using the most secure, impenetrable device known to man, I'm just saying that using the older technology can keep you safer most of the time. My father, for instance, runs his laptops using outdated MS operating systems purely because there aren't any viruses being written for those platforms anymore.
One of the more disappointing aspects of current gen tech is that, when you're buying something, you have to accept that there's now a large risk that you're vulnerable to a cyber-attack of some kind. It then becomes a matter of what you keep on your phone, rather than how to keep people out. Always maintain a mindset of, "If I lost my phone today or had it stolen, would it be a catastrophe?" If the answer is yes, rethink what you're putting on your devices and why.