Absolutely. At the very least, people who permanently plant themselves over the line of what would be considered normal/average positive behaviour and can be found in a constant state of extreme sanguineness are annoying. For the majority of us who are susceptible to foul moods, have bad days, and are affected by the various lows of life, the always upbeat person may appear to be mocking us, presenting his/herself as better than us, as uncaring and/or minimizing our feelings and struggles, and possibly lead us to feel even worse for not having the same level of apparent strength and optimism.
It is also not healthy to unfailingly view the world through rose coloured glasses. The unfortunate reality is that life deals us shit sometimes. We are built to react to the less than stellar times – break-ups, death of a loved on, goals not reached, bad hair days…. If a person’s mood never crosses over to the side of doom and gloom, they are in denial, suppressing, or have some serious mental health irregularities that need addressing.