If you're going to fail, you should at least fail when you're trying, rather than because you were too scared to try in the first place. If you were brought up to expend a lot of time and energy thinking about everything and making sure you had researched every angle before embarking on any kind of project, the big danger is that you fail to spot open doors. Or perhaps you spot them, but they light up all your defence mechanisms.
You spend time thinking "I wonder why the door isn't closed? Who failed to close it? Is anyone watching me as I size this situation up? What immovable obstacle or great calamity might be behind it? Remember what happened last time you went through an open door?" A child would just push the door open, take a look and go through. This is both delightful and efficient. No time is wasted. There's probably nothing behind the door anyway, in which case the child moves on. But if there is something, the engagement is candid and simple.
So when you're done with strategizing everything, weighing up risk/reward ratios, making sure that you have your exit route planned before you do anything, blame-storming before a project, or looking over the shoulder of the person talking to you in case someone better comes along, don't forget to push a few open doors, simply because there may well be a bite of life behind them. Maybe God leaves doors open, to encourage you to enquire. Or perhaps because he's old and forgetful (his biggest mistake is thinking he's in charge).
A friend of mine commented recently about how, as you get older, you realise that the rules start to become guidelines, guidleines become advice, then in some cases even the advice vanishes like a mirage in the presence of the vigour, the challenge, the salty taste of life. And since the kingdom of heaven is made up of people with childlike simplicity and trust, pushing a few open doors might just usher in the next thing we need on our journey home.