Your motivation is gone. What’s the point in doing anything? Nothing has any intrinsic meaning, which saps the little life energy out of you that remained to guide you to your goals. Welcome, my friend, to the world of nihilism.
The reason this belief (which I share, in case you’re interested) is so upsetting is that we’ve been living life unaware so far. It’s like the world has gone from telling you “this is what you should do with your life” to “I lied, you’re pointless”. This is one reason people like religion so much – they’re told that their life has divine meaning.
As Forest Gump famously said, “life is like a box of chocolates”. By this I mean that there are lovely sweet things in it that only give you short-lived pleasures. When you open the box of chocolates, you are fully aware of this. You don’t expect the chocolates to have an intrinsic meaning or to last for more than a few moments. You know the pleasure is fleeting, but you accept this and enjoy it anyway. Conquering nihilism is much the same; accept your life is meaningless and impermanent, but gobble up the good bits regardless.
One of the good things about nihilism is that you realise that all your mistakes will eventually be forgotten. You could do something as terrible launching a nuclear missile at the centre of London (please note that I am not giving you permission) and in the end nobody will even know London ever existed.
Another good thing about nihilism is that no life goal is less meaningful than another; you could decide to collect every red stamp feasibly possible and this is no less worthwhile than pursuing a high-paying career. The same can be said for changing goals; there was nothing meaningful to be gained from your previous goal so there’s nothing lost when you change it.
In conclusion, make meaning land wherever you want it to. Live life free of a deity dictating what you’re supposed to do. You can do whatever is within your means, which notably includes extending your means for the sheer sake of it. Learn to live life because you can, not because you have to.