Did you create your budget in gloomier days? Be aware there's new reason for optimism -- and for making mid-year tweaks to your budget. A few phantom green shoots a couple of years back aside, it’s been a long time since entrepreneurs had much in the way of positive economic news to celebrate. But while it’s still not exactly boom times, author and business expert Ram Charan may have finally located a reason to feel cheery. What is it? Turns out many businesses’ budgets for this year are too pessimistic, he writes on the HBR Blog Network . "There are plenty of reasons to be optimistic about the economic outlook for the next five years. The shifting energy equation, for example, sets the stage for growth. Shale gas will allow the US to be energy independent, create an export industry, and reduce energy costs.…