Yours truly is a huge fan of the Mission: Impossible movie series. They have it all - edge-of-the-seat action, missions, agent stuff, car chases, running chases, troubled characters, you name it. It's the perfect intelligent popcorn movie, all things Nolan not considered. It's has the comedy. It has the drama. It has everything.
Naturally the sequels differ from each other slightly in terms of quality of script, but one thing is constant: Ethan Hunt doesn't have the word 'impossible' in his vocabulary. Even if everyone else in his team tell him, quite convinced, that something cannot be done, he barely listens. I remember him doubting the success rate of a mission only once - when he was told he had to hold his breath for three minutes underwater while doing some data swapping. And even then he did it. (It's a nerve wracking scene, I must say.)
This kind of mentality rings a bell deep in my mind. I didn't always think like this but nowadays it's in the very core of my world view. I sometimes even get into arguments about this, for example if someone says something like "you can't sleep for four hours a night" or "you can't have a functioning society without taxes" or "you can't study every subject at school".
Can't you? Are they saying it's impossible, or that you'll die if you do it, or what?
Just because something is really hard doesn't mean it cannot be done.
I know Hunt is just a fictional character and the things he does are truly amazing and incredible (and he should have died at least ten times already), but it does not mean the metaphor isn't true. Attempting to do things everyone else said to be "impossible" is exactly the reason why people have visited space and built skyscrapers and bridges and why people fly airplanes and have computers. And sometime in the future there'll be things that the masses consider impossible today.
And even if you're not going to build a teleporter, you may have thought to yourself that you cannot start your own company while having kids or run a marathon with a bad knee or climb mount Everest without eyesight. It might be really hard but it isn't impossible. Very few things are.
So instead of automatically rejecting an idea as impossible, figure out how to do it. But don't waste too much time planning. Don't wait for the "right moment". Just go!