Sandra L. Schneider said this quote

If we define optimism broadly as the tendency to maintain a positive outlook, then realistic optimism is the tendency to maintain a positive outlook within the constraints of the available measurable phenomena situated in the physical and social world (DeGrandpre, 2000, p. 733). With respect to fuzzy meaning, realistic optimism involves enhancing and focusing on the favorable aspects of our experiences. Examples include being lenient in our evaluation of past events, actively appreciating the positive aspects of our current situation, and routinely emphasizing possible opportunities for the future. With respect to fuzzy knowledge, realistic optimism involves hoping, aspiring, and searching for positive experiences while acknowledging what we do not know and accepting what we cannot know.

~ Sandra L. Schneider

Appreciation involves being alert to the positive aspects of the current situation and feeling thankful for what one has and for one's circumstances. This requires not only a positive perspective in the present but also conscious awareness of features in the surround. The latter, in fact, is something that may be surprisingly rare. Especially when we are engaging in routine activities, we often do so mindlessly (Langer, 1997) or as though we were on automatic pilot (Cialdini, 1993). If we learn to bring our attention to the current state, we can choose to focus on positive aspects of the situation and to remind ourselves of the potential sources of good feelings that might otherwise pass unnoticed.

~ Sandra L. Schneider