How often do we talk about second thoughts? Maybe there is merit in capturing your first thoughts. Try this: (adapted from Writing Down the Bones by Natalie Goldberg) 
The basic unit of writing practice is the timed exercise. You may time yourself for ten minutes, twenty minutes, or an hour. It’s up to you. At the beginning you may want to start small and after week increase your time, or you may want to dive in for an hour the first time. It doesn’t matter.
What does matter is that whatever amount of time you choose for that full period:
These are the rules. It is important to adhere to them because the aim is to burn through to first thoughts, to the place where energy is unobstructed by social politeness or the internal censor, to the place where you are writing what your mind actually sees and feels, not what it thinks it should see or feel. It’s a great opportunity to capture the oddities of your mind. Explore the rugged edge of thought. Like grating a carrot, give the paper the colourful coleslaw of your consciousness.
First thoughts have tremendous energy. It is the way the mind first flashes on something. The internal censor usually squelches them, so we live in the realm of second and third thoughts, thoughts on thought, twice and three times removed from the direct connection of the first fresh flash.