It’s not hard to break into a tangent in thought or speech. What I’m considering is that our tangents are greater ideas born from the middle of a conversation.
Think of it as such: we have to give opinion to a conversation instantly, without that time for proper thought – and yet, within our minds, possibly in the subconscious that is still brewing to come up with these ideas, there is a solution to the conversation. However, this does not come about as quickly as one might like.
It’s just as the phenomena of acoustic hesitation. We may hear the words someone says, and, if they are particularly rushed, we may reply with a “pardon?” or “what did you say?”. However, as we are speaking, we come to realise just what it was that they have said, rendering their repetitions moot.
Why does this happen? It is the time it takes our minds to untangle the string of words into coherent language. In the same way, it is possible that our minds are still unravelling the strings of a decent explanation or reply whilst we begin to talk or let the internal monologue dictate a piece of writing.
This is why our best ideas can come after writing a whole load of rubbish; something that appears to be random is actually well devised through the subconscious digging deeper into our collection of knowledge. Perhaps it has even been adapting the current stimuli – bouncing ideas off someone else, as it may be.
This is not, however, to say that ideas of the beginning of a speech, or those with preparation, are less important than the ideas that come mid-flow. In fact, preparation and renewal of idea leads to a firmer foundation for speech and conclusive decisions. Which is why it is a more successful way of going about working.
From self-evidence, tangents have seemed to contain the richest veins of intellect or idea, regardless from where the conversation may have begun.
 This also relates to the previous 'Transferral Route'