twice as good or double trouble

Twice as good or double trouble ? (Is making doubles twice as good as the original or can it make double trouble? 它会带来两倍的好处呢？ 还是双倍的麻烦呢？)
Tom works hard, and John as hard.汤姆学习刻苦，约翰也一样刻苦。
His income is double what it was five years ago. 他的收入是五年前的两倍。

这是谚语：福无双至，祸不单行。

双倍的福还是祸不单行