Doubt
If I had a magic wand, I would love to wave it around and remove people’s doubt. People spend way too much time considering all the reasons something won’t work rather than focusing on all the reasons something might actually work.
“What if it doesn’t work?” is the cry of many people, mid dream. As an annoying 'positive polly', “What if it does?” is my favourite response!
'Negative nellys' hate this. They are way more attached to a negative outcome than a positive one! Negative outcomes are way easier to manage - many people actually feel safer with them.
Marianne Williamson’s quote written for Nelson Mandela's inaugural speech states:
“Our deepest fear is not that we are inadequate.
Our deepest fear is that we are powerful beyond measure.
It is our light not our darkness that most frightens us.
We ask ourselves, who am I to be brilliant, gorgeous,
talented and fabulous? 
Doubt is often fear dressed up as logic. Doubt makes you think you're being sensible, careful, wise. It tricks you into believing that more thinking will lead to more clarity. But it's not always the case.
Doubt keeps us small. Doubt stops us from living.
Overthinking and self-doubt are close relatives. Overthinking often comes from under-feeling. When you're trapped in doubt, you're usually trying to think your way out of something you need to feel your way through. Your head is doing laps whilst your heart and gut are screaming at you to move.
I’m a big fan of giving things a go. In the 90’s, I worked for an adrenaline sports company called NO FEAR. We sold a tee shirt that had “There is nothing more painful than regret.” That rang true for me.
I am not big on regrets. I look at things two ways - a win or a lesson. There are so many things we can learn from giving things a go. Experience, knowledge, and resilience are all benefits of giving things a shot.
I spent years watching people being trapped in their heads, paralysed by doubt. The ones who doubt whether they're good enough to start that business. The ones who doubt whether they should have that conversation. The ones who doubt whether they deserve what they want. And while they're doubting, life is happening. Time is passing. Opportunities are vanishing.
What would you do if you allowed NO doubt? 
If doubt was not an option?
Certainty is a myth. You're never going to be 100% sure. You're never going to have all the information. You're never going to feel completely ready. Waiting for perfect conditions is just another form of doubt.
I've done plenty of things I wasn't certain about. And even when things didn't work out exactly as I planned, I was still OK. Because taking action, even imperfect action, is better than drowning in doubt.