TFTD

Is it unrealistic to look at the bright side, to remain generally positive, and to expect the best in life?

No, because reality itself is neutral, and what you get from it depends upon how you view it and what you make of it.
The raw forces, circumstances and events are, for the most part, out of your control.

Yet you can completely control the way you perceive, respond, adapt and yes, even prosper under their influence.
The control you exercise over your own perceptions, thoughts and actions will make all the difference in your life.

Reality is what it is, and your own relationship to that reality is precisely whatever you choose for it to be.