Don't make a mountain out of an anthill, it's not a big deal.
She always makes a mountain out of an anthill, turning a small mistake into a huge one.
He tends to make a mountain out of an anthill, blowing minor issues into major problems.
Stop making a mountain out of an anthill, it's not a serious issue.
She has a tendency to make a mountain out of an anthill, always seeing a small situation as critical.