The problem with the consequences of our actions is that you don’t have to deal with them at the moment. Quite often, you can push them back for a different day.
Eating one marshmallow (such as sweets, cigarettes, not studying for a test…) doesn’t cause metaphorical diabetes or cancer. But do it again 10,000 times and then you have to live with the consequences.
It’s easy to say yes in the short-term because that’s the moment we live in. And since we only live once, it’s difficult to imagine a world without us in it.
The challenges are not things like climate change, these are side effects. The challenge is saying no to the thrill of instant gratification. It’s investing into tomorrow today.