Interesting that many people are getting this wrong.

The original is "grit and bear it". Many people don't know the word "grit" in this context". It means to "hold your teeth together" or "clench your jaw"... this is what humans do automatically when something unpleasant happens.

"Grit and bear it" means to clench your jaw and deal with the unpleasantness.

"Grin and bear it" is an eggcorn.

I'm a Nut

Written By: Unknown

Copyright Unknown I'm an acorn, small and round

Lying on the cold, cold ground

Everyone walks over me

That is why I'm cracked you see

I'm a nut!

(Click, click with tongue)

I'm a nut!

(Click, click with tongue)

I'm a nut!

(Click, click with tongue)

Called myself on the telephone

Just to hear my golden tone

Asked me out for a little date

Picked me up about half past eight

I'm a nut!

(Click, click with tongue)

I'm a nut!

(Click, click with tongue)

I'm a nut!

(Click, click with tongue)

Took myself to the movie show

Stayed too late and said "Let's go"

Took my hand and led me out

Drove me home and gave a shout!

I'm a nut!

(Click, click with tongue)

I'm a nut!

(Click, click with tongue)

I'm a nut!

(Click, click with tongue)