Forbear (v): to refrain from, to abstain

John told me I could  become a  millionaire if I joined him in his business, but his lack of integrity makes me nervous so I decided to forbear.

 

Forgo ( v) to do without, to forbear

We decided to forego the chocolate-covered potato chips.

Forsake ( v) to abandon, to renounce, to relinquish

We urge Buddy to forsake his life with the alien beings and return to his job at the drugstore.

Fortuitous (adj) accidental, occurring by chance

The program’s outcome was not the result of plan but was entirely fortuitous.

 

Founder (v) to fail, to collapse, to sink,

The candidate’s campaign for the presidency foundered when it was revealed that she had once been married to a drug addict.

Frenetic (adj) frantic, frenzied

There was a lot of frenetic activity in the office, but nothing ever seemed to get accomplished.

 

Frugal (adj) economical, peeny-pinching

Mina was so frugal that she even tried to bargain with the checkout girl at the discount store.

Furtive (adj) secretive, sly

The burglars were furtive, but not furtive enough

Futile ( adj) useless, hopeless