Don't give up just because of what someone said. Use it as motivation to push harder.

We can let our past [difficulties and failures] beat us or teach us [to be more knowledgeable, competent and realistic in the future]!

It's impossible to consistently behave in a manner inconsistent with how we see ourselves. We can do very few things in a positive way if we feel negative about ourselves.

You can get everything in life you want if you will just help enough other people get what they want.

If you're sincere, praise is effective. If you're insincere, it's manipulative.

You are the most influential person you will talk to all day.

It might interest you to know that the 1828 Noah Webster Dictionary identifies the optimist in complimentary terms, but says nothing about the pessimist. The word 'pessimist' was not in our vocabulary at that time. It's a modern 'invention' which I believe we should 'dis-invent.'