Instead of changing your attitude about life or reading books, consider spending time to develop better core cognitive skills.
Unlike getting tutoring or just studying more, this effort improves the basic mental components that support the overall thinking process. Functions like visual and auditory processing, working and long-term memory, attention & focus, logic & reasoning and processing speed to name a few. A weakness in any single one of those areas can thwart a person's overall ability to learn. When those things get better a person has increased confidence in approaching unfamiliar things, allowing them to make more considered choices in their responses.
For example, often a person who struggles merely has a problem with properly hearing spoken language. Sure they can hear words and know their meanings but if they have a hard time processing the input fast enough they might not be able to recognize and make proper sense of them. One might say it is like not being used to a thick accent. If you can't get the words it doesn't matter how smart you are, you won't have all the data necessary to interpret the situation. Or maybe it's like not knowing enough of the slang or jargon. Incomplete or bad data can leave you confused, especially if you have an inkling you're missing something. Kinda hard to think clearly when that happens.
Anyway, that's just one example. You can imagine other ways thinking becomes difficult, like when you have poor working memory. If you can't keep track of the data you can't make consistently accurate conclusions. Again, you might be aware of that problem and anxiety & self-doubt can build over it thus inhibiting your thought process even more.
All those things I listed above work together to support higher level thinking - and they're applicable on a global level, not just being able to do math problems in your head or make snappy comments in the moment. Getting better input from all your senses gives you much better materials for your brain to work with when thinking about pretty much anything.
Another way to improve your thinking is to change your approach to listening or reading. Listening to understand rather than listening to reply is better in the long run. Geez, that sounds like a cheesy meme but it's true.
-Peter Wick, PhD in Pharmacology