It's worth remember none of can really know anything. Including that fact.
Everything could be undermined starting tomorrow, and you have no way of knowing if it could happen. The only answer is to remain pragmatic (not nihilistic) and just keep on going. Point is, there really is no point thinking your ever secure because there is no such base to build your edifice of knowledge on.
An example and interesting mental exercise: Think of something that for your entire life has been constant - i.e. the sky is blue. Now can you be 100% certain it will be blue tomorrow? I think not. All of experience, history and current science indicates it will, but who's to say the rules won't suddenly change tomorrow? Nobody. No matter what they say.
Anyway. It's all absurd, but we can still do a fair amount in the framework we do have. Namely, (in my opinion, which is never so humble), try to be as zen as possible, see the good in everything and try to do anything possible to make this "solitary, poor, nasty, brutish and short" existence as free from such things as possible for not only you but every other beating heart on this planet who is capable of empathy.
If you consider that to be akin to something a hippy would say then you simply have no imagination. "Hippy" is an outmoded term and means, to me, precisely dick.
All you need is love.