How do you secure your bootloader unlocked device?

I have a brand new Nexus 5, unlocked and rooted. It obviously has security risks and I understand that. If I lose my phone, anyone can go into recovery mode, backup my data and get access to my data which is a huge security risk.

I'm wondering how people secure their boot unlocked device?

a) Re-lock the bootloader permanently once rooted?

b) Use root apps like "Bootloader Unlock" to lock/unlock on demand?

c) Use Android's phone encryption?

d) Any other technique?

I'm not much of an Android person as I have been using my Nexus 5 rooted/unlocked for only a week or two. So what the more knowledgeable veterans here do to secure their devices?

Thanks.