I find it hard to offer advice to new parents, its a mix between feeling like you want to share all your experiences, but not wanting to a) petrify them, or b) come across as someone who thinks they know it all. I try and avoid giving advice until it is asked of me, for the above reasons, but another thing I have learnt, is that people often won't ask.
So... what is the one piece of advice I would give to every new parent?