Those imminent-brain-imploding sensations otherwise known as headaches are probably the worst.
But what actually is a headache? And what causes them?
There are actually over 200 different kinds of headache, and most of us will experience one at least once in our lifetime. Oh joy!
Primary headaches (AKA the more serious kind) make up over 90% of headaches and, generally speaking, these are not damaging to your health.
Secondary headaches on the other hand are far more serious and could be caused by underlying health issues such as inflammatory disease, meningitis or a brain tumour. It's worth noting however that these are very uncommon.
Why, oh why, do headaches hurt so much?
While it might feel like your brain is in pain, it's actually the inflammation of blood vessels, which cause irritation and swelling of the meninges (the tissue covering the brain).
Tension headaches are often caused by daily stresses and tensions - for example, if you've slept on your neck strangely or perhaps you've been sitting with bad posture at work. These will trigger inflammation in your noggin' and, hey presto, you've got yourself a headache.
Similarly, this also happens when blood vessels come into contact with cold food and beverages such as ice cream. Hello brain freeze.
And if you've tried to go cold turkey when it comes to caffeine, then you'll probably have experienced a headache from that too.
A study suggests that this is because when your body is lacking caffeine, the blood flow to your brain increases. Ugh.
So how can you relieve the pain? Put some Enya on, lie back and relax. (Or reach for the paracetamol.)