Discipline
The Abbility to observe the market for what it is. Fitting yourself/your method to the market rather than the other way round.
Maby?
Of course money management is not a characteristic, rather it is a trader's skill, but in my opinion it's one of the most essential criteria that determines if the trader will be successful or not in the long run. Incidentally, money management principles may be useless if one does not have subject to comply with them.
For myself, the ideal characteristic was understanding how to listen. I accept losses as opportunity and attribute any success.
My egy is one of development. I have 2-3 plans for both the bullish and bearish bias with long term outlook on each trade and I handle it very severe, with no emotional connection.
When your able to remove your senses and emotions while looking at the market you may see it for the very first time. You might even see something else also. Only gotta clear your mind and listento.
Of course this type of mentality has to be practiced to a perfection while knowing there isn't any perfection.