Are Left handers servants of the devil? For thousands of years, the Devil has been associated with the left hand in various ways and is normally portrayed as being left-handed in pictures and other images.

In the seventeenth century it was thought that the Devil baptised his followers with his left-hand and there are many references in superstitions to the "left-hand side" being associated with evil.

We say "do the right thing" thus favoring the right side to the left one. Jesus is portraited using his right hand and on the contrary, Devil using the left. 

What are the traditions of the Church towards left handness?
Traditionally, and not just in the Church, the right hand was considered more "noble" than the left, probably just because there are a lot more right-handed than left-handed people.  As a result, the Church's traditional rubrics specify that some ceremonial actions be performed with the right hand, even if the person performing them is left-handed. For example, I believe priests are supposed to distribute communion with the right hand.  This also applies to some actions that are not strictly governed by rubrics; for example, even though I'm left-handed, I make the sign of the cross with my right hand. 

Until fairly recently, this sort of preference for the right hand was much more visible in secular society too.  For example, my father, who was (like me and two of my four siblings) left-handed, was forced, as a child, to learn to write with his right hand.  The preference also shows up in the English language, not only in phrases like the ones you mentioned in the question, but also in single words like "dexterous", "ambidextrous", and "sinister".

Finally, to answer the original question: No, I'm not a servant of the devil.