a best friend
A best friend is someone who will stick with you even when you’re being a total mess and also tell you when you’re being a total mess.
You: 'I failed my test.' Best friend: 'You failed your test and your life.'
You: 'I spilled my lunch.' Best friend: 'I spilled my life.'
You: 'I’m a mess.' Best friend: 'You’re a mess, but you’re my mess.'