Prevent OR stop

samerrustomWhich one shall I use?

These:

I prevented/stopped my little brother from going on a trip with some bad guys.
I stopped/prevented my brother from talking to my girlfriend.
I stopped myself from eating junk food,

Thank you.
I haven't noticed any difference in meaning In the first and second example. Why did choose stopped instead of prevented in the third example, could you explain please?

Which one shall I use in a formal business emails?

samerrustomWhy did choose stopped instead of prevented in the third example, could you explain please?

It sounded wrong. Most differences in close synonyms are collocation-related.

samerrustomWhich one shall I use in a formal business emails?

Both are possible. Things that are stopped after they start cannot be prevented.

Thank you.

I think I got it.

Can I say " I stopped traveling when I became 40 years old"?
Can I say " I prevented my dad from buying a new car because he doesn't have the enough money and I can't lend him"

samerrustomCan I say " I stopped traveling when I became 40 years old"?Can I say " I prevented my dad from buying a new car because he doesn't have the enough money and I can't lend him"

Yes, you certainly can.