Your information diet. Social media. Gossipy and negative people. Mulling over old failures/regrets/slights etc. The mind is easily pulled along by negativity and outrage... as can be observed in our current global psychological state.
Don't be so pessimistic about your own ability to control how you process information, you can control this a lot more than you think, apparently.
This does not mean to ignore things that are unpleasant, but rather to not allow things that do not benefit your diverse goals to occupy your productive potential, focusing instead on things that inform your path, actionable and relevant information, tools rather than distractions.
Yeah, I think I do more or less the same as you describe, except my barrier to figuring out what is "not useful to my purposes" requires it to first exist in my mind for a while, before I can discard it as not applicable, as sometimes seemingly random things in one context somehow relates to completely different things.
I've chosen to do stuff sometimes that made no sense besides "It's fun but a waste of time" and it ended up leading me to realizations and experiences I wouldn't have had otherwise. But if I focused too much on avoiding things and optimizing "what I let in", I'd never be open enough to learn what I didn't know I could learn from it.
You actually do most of the times. It can be a conscious choice with surprisingly positive outcome. Choosing not to use social media, read news, disable push notifications and so on, go on information diet and this may not only make you a happier person but also increase your ability to filter useful information.