There are few things more frustrating than being woken before you're ready.

You might be disturbed in the night by children, noise, heat or travel. You might wake too early when the room starts to brighten. You might sleep lightly because something keeps pulling you out of rest.

However it happens, broken sleep leaves its mark.

Morning comes too soon, and you wake feeling tired, irritable or unrested.

It can be a night that starts badly because you struggle to switch off. It can be a restless patch in the middle of the night. It can be an early morning wake up that comes long before you feel ready.

By the time you get up, it can feel as though the night never really gave you the rest you needed.

Sleep is influenced by many things, including stress, routine, exercise, hydration and screen habits. In this guide, we're focusing on one part of the picture you can control directly: your sleep environment, starting with unwanted light.

It's also shaped by how deep your sleep is, and how often you are pulled out of it.

Light is one of the most important signals your body uses to understand when to wake and when to rest. That is why even ordinary sources of light can matter: a streetlamp outside the window, a phone screen beside the bed, early morning brightness, or a hotel room that never gets dark.

When light keeps reaching you at the wrong time, it can make broken sleep harder to recover from.

So if you are waking tired, it may not be because you are doing everything wrong.

YOUR SLEEP ENVIRONMENT MAY BE QUIETLY WORKING AGAINST YOU.