[Edit: Just wanted to say that I only posted this here because I think this is a very good thread topic and that this is genuinely a quote that has influenced my trading philosophy greatly, and thought it might help others too - but it is not an entry to this competition linked with this thread 
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There is truth in the saying that ”a picture is worth more than a thousand words”, and there are endless quotations that do precisely that by creating a mental picture that concisely sums up a situation that would otherwise take many words to describe.
But my most memorable words were not actually about trading nor were they directly spoken to me (thank goodness, since they are attributed to a John A. Shedd in 1928! 
). It is a quotation that, for me, embodies everything that is intrinsic to successful trading.
The quotation runs:
”A ship in harbour is safe – but that is not what ships are for”
In a trading sense, our ”ship” is our capital and the ”harbour” is the account in which we keep it – and the seas are the markets in which we are going to sail her.
This adage has become a deep, personal motto for me and it always reminds me of what my trading is all about. As a trader I have designated a certain amount of capital to fund my activities and I have entrusted it to a broker account for this purpose. But whilst it is (relatively) safe lying dormant in that account it cannot achieve its purpose unless I am actively sailing in the seas of the markets that I choose to trade. You cannot profit unless you are in the market.
We must first understand that we are the sole captain of our ship and entirely responsible for its safety.
And before we set sail we have to check whether our ship is seaworthy and suitable for the kind of forces present in the seas (markets) in which we want to sail.
We have to understand how our ship works, its strengths and weaknesses, its capacity, and its maneuverability and vulnerability. In the trading sense this refers to knowing one’s capital adequacy, risk exposure, money management criteria, the implications of leverage, the positioning of sensible stops and targets, etc.
But we also need to understand the nature and characteristics of the seas themselves upon which we are going to set sail. Its tides and currents, the storms and the calm, the height of its waves, its coastlines, channels, markers and harbours. In the trading sense, we need to select our markets with care and understand their character and the risks as well as the potential.
But, as captain of our ship, we also need our personal skills. No seaman sets sail without navigation instruments and the skills to use them. One has to know the rules of the oceans as well as how to control the ship in all weathers. We need to be aware of our own character and our strengths and weaknesses and gain practical experience of how to ride the storms and the unexpected and not just rely on fair weather sailing.
As traders we need to learn our trade. We need a method that we can both understand and implement. We need to understand how to employ leverage and when are the best times to set sail and when to leave the anchors down……and we really need to understand where we want to go and how we intend to get there.
So, all in all, once you know your capital requirements, understand the risks you are facing, understand your method and know where your targets are and have developed your skills as a trader then you ready to say:
”My ship in harbour is safe – but that is not what my ship is for”
Then all that remains is to wish you ”fair winds and following seas” 
PS. This won’t be the best post here - but it will certainly be the longest! 
