In the practice of mettā meditation, it is best to start with yourself, before radiating mettā to others. A lot of the difficulty people find in feeling mettā for themselves may be avoided by choosing words that have particular meaning to them. There is no need to keep to the traditional formula. Personally, for example, I find the phrase, 'May I be happy' unhelpfully vague, and never use it. The best phrases are those which express our highest aspirations. Here is an example of one set:

'May this body be healthy and well;
May I know the happiness of good health.
May patience grow within me;
May I know the happiness of a patient mind.
May loving-kindness grow within me;
May I know the happiness of a kind, loving mind.
May mindfulness grow within me;
May I know the happiness of a mindful mind.
May peace grow within me;
May I know the happiness of a peaceful mind.
May wisdom grow within me;
May I know the happiness of a wise mind.'

- Ajahn Jayasāro