OK, so saying you're going to be positive is easy enough - sticking to it is another matter!
When you're stuck in a rut and those negative thoughts make their way into your mind, take a minute to banish them.
Lynda suggests several techniques for injecting a feel-good buzz into your life.
"Having things written down is a good idea," she says. "I’m good enough’; ‘I’m a success’; ‘the world is beautiful today.'"
You can write these down and stick them on your walls, or keep little cards of positive thoughts in your handbag or pocket.
Then next time your boss gets mad or you have an argument at home, remind yourself that you're actually amazing.
Taking a minute to appreciate the world around you is also a great way to bust those self-esteem blues. Put things into perspective and recognise that you're lucky.