Two Extremes of Metta I've practiced metta, or attempted to, with mixed results. 

Sometimes I'm wondering even how to practice metta, and in my mind it feels like I'm just repeating "How can I develop compassion? How can I develop compassion?" It's almost a lack of contact with the feeling of compassion, or just tedious repetition.

However, sometimes, at other times, I feel extreme feeling of compassion, to the point where I clench my jaw to avoid the feeling (since seemingly I am very repressed). It's a mixture of being moved, and compassion, since it arises when I react to either moving events, or when I see someone suffering. But, admittedly, it's really being moved that generates the most feeling.

I have sometimes managed to generate such a feeling in meditation by visualizing people doing acts of kindness, myself included. However, whenever this happens, I feel that the feeling isn't enough, that compassion should require effort.

Is this the case? Does a feeling of being moved, or a compassionate intention and feeling, generate something positive? Or, am I right in thinking that without effort and discipline, these feelings are merely oceanic and vast but not linked with true mental development?

Also, I suspect I might lack self-compassion or something because I don't allow myself to feel these feelings, and I often--used to--feel being undeserving of all these things. Any thoughts?

Thanks

PS: I recall a Buddhist teacher reacting to my yearning to develop compassion with enthusiasm, but advising against body meditation because it could be detrimental. How could I know if metta meditation is best for me? Any signs?
Repeating the words many times over might help you remember to do Metta when it is needed in a difficult situation. As a form of Metta it is very shallow, but nevertheless maybe beneficial. If you develop aversion when doing this best not do it at such times. When you get fed up just stop. Also the repetition may serve the basis for a change in attitude.

The most deeped way to do it is do Vipassana or Samatha Meditation. At some point you might get a pleasant feeling. When this happens bring ups the wish that others also experience this peace. This is more deeper form of Metta.

Objective of Metta is to:


develop and increase qualities Metta
break barriers thereby you consider some people of class of people more favorably than the others