I don't believe it can be stopped at all.
I think the only way to lessen the problem is with education. Otherwise, I can only think that the only way to stop the attacks, sadly, is by joining them.
Exactly, there's no way from stopping crazy extremists from blowing themselves other than trying to educate them and show them that perhaps that's not the most productive thing they should be doing.
It doesn't matter how much security staff you employ, how many security measures you implement or how many people or vehicles you search - someone can always get through and blow themselves up.
And considering how unlikely it is to be the victim of a terrorist attack (at least in Western countries), the best thing to do is just to not worry about it. In the UK, you are more likely to die from a furniture accident than from a terrorist attack.
The media love a terrorist news story, because it's scary and gets loads of people reading it and riled up. Terrorists are a bit like internet trolls IMO, the best thing we can do is ignore them as much as possible - by publicising their attacks we are fueling the fire for more of them to get on the bandwagon, which is exactly what they want!
