I myself prefer Realistic view .If you imagine a situation better or worse than what it is, or even imagine a bad situation better or good situation worse than what it is ; you may make mistakes in making "right" decisions...Although, optimism can help us to have positive thinking and may increase motivation in most cases...

Sometimes in life we are persistent in choosing a wrong choice, as for example when we are persistently confident in tax evasion. Many people have been very optimistic, that tax evasion and bribery would maintain their financial prosperity vivid, but after a certain time all those people prove to have been wrong and have to face the severe consequences. So, sooner or later, in times when people persistently follow a wrong, illegeal or immoral manner, being optimistic about the outcome of their decision always proves to be disastrous to themselves. At the end, I think that obsessive, passionate optimism, can indeed turn out harmful to one's self. On the other hand I don't think that people can ever benefit from being pessimistic, at all. Pessimism is the root which grows the tree of desperation, and a desperate person is harmful to his/her surroundings in many ways. There's always got to be some hope in our hearts for the better. People are not made to be desperate, people, within the human nature, are made to be evolving and improving within their own entity and towards their environment and surroundings. The ideal condition is being always rational with a wide logical awareness of the conditions that affect ourselves and have a moderate or strong tendency to optimism, a tendency which turns life sweeter, a life worth living.

It depends on whether you are an optimist or pessimist!

it's too simple to divide people into optimist and pessimists. I think alot of people that claim that they are optimists, often are fake, and people that claims to pessimist in reality are control freaks. Why? Because they think that by being a pessimist, they will never be suprised by anything, because they always have a negative view of things. Personally I like to avoid both (optimist and pessimist claimers), because they are introverted people.

Thank you all. My sincere thanks to Paul, mimosveta, stevecritchley256, Jura, manos, and Jacob for answering my question. I think too much optimism and too much pessimism aren't good. We need to achieve a balance of being optimistic and pessimistic. Although we need to be hopeful and expect the best when we face difficult situations in our lives, we also have to be realistic about the things that we can't change and avoid pipe dreams.