I actually think people mock positive self-talk because it makes us uncomfortable. We're embarrassed to say positive things about ourselves, and afraid to "jinx" anything by saying positive things about the rest of our lives. We're also loathe to delude ourselves into thinking something positive (about ourselves or anything else) that isn't "true." Clients experience the same barriers. However, discomfort lessens with practice (rather than avoidance), and "positive" doesn't have to be "Pollyanna." There are plenty of positive things that are absolutely true, and it's often enough for self-talk to be just a bit more positive than our usual thinking.
That said, I think of positive self-talk in two main categories: Affirmations and Aspirations.
Affirmations affirm what is already true. That includes things you might not usually recognize or acknowledge, might minimize or otherwise discount. For example, you might affirm that you are intelligent, compassionate, funny, etc. You can also affirm your values, ideals, and commitments. Mottos fall into this category, such as "it is what it is," or "where there's a will, there's a way." Likewise, people affirm their commitment to recovery, with self-talk such as "recovery is hard, but I can do it," or "I am moving toward health." Perhaps the most famous illustration of affirmations is "The Little Engine That Could." Affirmations balance out all the self-criticism most of us engage in, make us more hopeful, more likely to take action toward goals, and better able to bounce back from set-backs.
Aspirations verbalize things that might not be true yet, but toward which you aspire. They tap into your hopes and ideals. You might think of a goal as if it's being achieved, for example "I'm landing a great job," or express qualities you aspire to as if you've attained them, for example "I am confident" or "fearless." These sorts of aspirations can be found engraved on stones or jewelry - totems of sorts. Aspirations can be give you an infusion of motivation and optimism to continue working toward those things to which you aspire.
What do you think about positive self-talk? How do you use it (with clients or yourself)? Are there other forms you can think of?