You must feel what you are creating, the physicality of the work, pour yourself into the container. What is on the surface is an illusion; it is within the vibration of color, the bending of space and time - your fluctuation of anxiety and calm - that will resonate with others. It is the energy of a creator, or channel of creative energies - whatever your preference is.
Great musicians memorize the music and spend their time interpreting it on their instrument - but they have already played the piece hundreds of times in their mind. The experience of performance is an emotional experience - that is what we hear and feel - it is not a struggle with their instruments or medium, it is not a questioning and hesitant series of statements.
Engage in a sense of mastery by making strong and deliberate marks on your canvas - be bold and decisive, even if that mark will be painted over, get in the habit of saying each thing with such confidence and commitment as to convince us that it is that mark and only that mark that you wish to make.
But above and beyond the technical choices, tap into your feelings and allow them to impress themselves into the paint, do not hold back and be caught up in the hard cold world of facts and rules. Use any means to get at your emotions - don't think you need to just face the canvas and call them forth on your own.
Movies, television, music, poetry, fiction, looking through old photos, riding the bus, people watching, whatever you have at your disposal - sometimes they are great for inspiring a new subject, but any of these can trigger emotions, some stronger than others. Whether they make you laugh or cry, get angry or peaceful, ride the wave and get your emotions flowing - forget about technique when you step up to paint, don't make choices, allow the choices to be made as a consequence of your emotional state and creative flow.
That's not to say that if you watched a tragic scene from a movie then you would paint a tragic painting - that isn't the point - the point is to feel deeply and experience that and other deep emotions while you are painting. The push and pull of light and dark forces will reveal an honest beauty through their struggle on the canvas and be far more profound than a one dimensional single statement piece. Don't just play the notes - play the music.