The downsides, as I see them, are - People take your optimism and flexibility as naivety and a lack of backbone. Also see Why is enthusiasm often perceived as naivety? – The perception that there’s always another chance may be healthy, but it isn’t always true. Finding out there is a finite amount of opportunities can be difficult. – Your actions and attitude affect others around you. As you gather people closer to you, that you either don’t want to lose, or can’t afford to lose, your built up history and reputation become more important. That includes whether or not you are perceived to care about your failures and shortcomings. – At some point, someone will be reliant on you. There may be flexibility from your perspective, but not theirs. All that said, the questions I come back to are what are the alternatives? A life of cynacism and planned, optimized, rigor? Do I prefer that? I always come back to optimism, because that alternative is no way that I want to live. It’s completely unnatural to me and probably to you. Just work on a healthy balance and realize what others see in your outlook and actions.