fainthearted

This is not the time to be fainthearted but to continue pressing the advantage.

But it's not for the fainthearted - or the claustrophobic.

The treatment wasn't for the fainthearted, even among its proponents.

However, life underground is not for the fainthearted.

In his telling, the prosecutors come across as fainthearted, lacking “energy” and “enthusiasm,” and “relentlessly negative.”