(informal, figuratively) Easily, without much effort. / (informal, figuratively) Hampered by factors outside one’s control.

To help in one way but proceed to harm in another.

Alternative form of one can't hold two watermelons in one hand

One should not attempt to take on more than one can handle.

Using only one hand.

The quality of having a dominant hand; left-handedness or right-handedness. / Chirality / The possession of only one hand or the ability to use only one hand; the loss of the use of one hand.