To be optimistic is to bless the present, trust yourself, and expect the best. To be pessimistic is to complain about the present, doubt yourself, and expect the worst. The difference is far more than simply two points of view, because each one produces different mental, emotional, and physical effects.
First, though, let's discuss the fact that we all have the ability to choose our points of view and to change those points of view. To use a classic example, if we fill a glass to the midpoint with water (or some other liquid) we can describe it as half full or half empty. We could also say that it doesn't matter, but in fact it does. Each of these viewpoints has an effect on how we think about the past and the future.
When we call a glass half empty there is a strong tendency to think of the empty part as something missing, used up, or not available. When we call it half full, there is a tendency to think in terms of filling it up, or completing an unfinished task. This is evident in related statements like, "It's already half empty" or "It's only half full." The same idea applied to a task might come out as "I've already done enough" or "I'm not finished yet."
In Huna philosophy we say that "Energy flows where attention goes," and "You get what you focus on." What this really means is that the way you focus your attention determines what comes into your awareness. A pessimistic focus is essentially based on fear. People complain because they are afraid that things won't get better unless they point out what is wrong. And yet the complaints keep the focus on what isn't good without leaving room to be aware of what is good. Self doubt comes from a fear that one isn't or won't be good enough for something, but it keeps getting in the way of getting better. And expecting the worst is a fear of disappointment, which is really just a decision that one doesn't like something that has happened. The deep purpose of fear is to avoid pain, but the techniques of pessimism encourage fear and actually produce more pain than necessary.
By contrast, an optimistic focus is essentially based on hope. Blessing the present brings goodness into awareness and encourages the hope that more will follow. Trusting oneself means believing in one's worth and capacity for coping with change. It is the hope that, no matter what happens, one will find some way of dealing with it in the best way possible. And expecting the best is the essence of positive action. What it encourages is the ability to find goodness, inspiration, knowledge, or creative ideas in anything that happens.
Energetically, pessimism inhibits the flow of ideas, pleasurable feelings, and healing. Complaints keep the focus on problems, rather than solutions. Self doubt keeps the focus on oneself, rather than including others. And expecting the worst keeps the focus on failures, and not achievements. Worse of all, everyone one of these pessimistic behaviors results in an increase of physical tension, which inhibits creativity, reduces emotional rapport, and lowers vitality.
To bless the present is to acknowledge, appreciate, and be grateful for whatever good you become aware of in your current environment. Because this refers to anything in your environment, it can include anyone or anything you think of or become aware of through media or other people. While most people will only focus on what they already think of as good, it is possible to expand your awareness of goodness to things and people and relationships that you wouldn't ordinarily pay attention to. I know it sounds strange, but I once attained a cosmic bliss state by appreciating the relationship between two paper cups on a table in the Santa Monica Mall. Some incredibly good benefits of blessing the present are physical relaxation, emotional pleasure, and mental expansion.
To trust yourself is to have no doubt about your worth or your capability for achievement. It does not mean that you have to do everything yourself. I once read of a trial involving Henry Ford in which his competence to run a company was called into question. When a lawyer criticized him for not knowing the names of all the US presidents, Ford said, "No, I don't, but I have a button on my desk that will call someone who can tell me if I need to know." There will be times, naturally, when you may not trust yourself to be able to handle something, and at those times mere knowledge or access to knowledge may not help. You will find, however, that almost always such lack of trust is due to too much stress. As you relax, using whatever means you can, you will find the trust returning.
To expect the best is to think that everything will work out in the best way possible. It does not mean to expect that everything will work out exactly as you plan. Sometimes it isn't that good, and sometimes it's a lot better. In our Huna teaching we have a saying: Everything's Working Out Perfectly" and we often use the acronym "EWOP" as a verb, as in "When we don't have any idea how it's going to turn out, let's EWOP it." That means, of course, to expect the best. Based on experience, we now usually say, "Everything's Working Out Perfectly (but maybe differently)." There is another variation: "Remember, Everything's Working Out Perfectly," which as a reverse acronym spells "POWER." Also, in bad situations, repeating this as an affirmation has very often resulted in what many people call miracles.
I'll finish this with the motto of Queen Kapi'olani: "Kulia i ka nu'u - Strive to reach the summit." As a note of interest, the Hawaiian word kulia not only means "to strive, to try," it also means "fortunate, lucky." Nu'u means "summit" and, figuratively, "the best you can be." And that goes along with another saying attributed to the Roman senator Seneca in the 1st century AD: "Luck is when preparation meets opportunity."