Especially in tactic trainer, when it requires us to find those quick and obvious moves within a short period of time; I get all worked up on finding the correct move and even going as far as checking to see if it was right (which I'm always wrong). While in reality there was no need to and the move was right there! I always fail at these problems, yet I can see the longer and somewhat harder ones that requires longer moves and a bit more time. Why does this happen? How can I get rid of this retarded overthinking mind of mine? Thank you!

Most the time, when we are given a puzzle, that we are unfamiliar with, Can solve a puzzle easier with similar patterns and if you remember it. Sort of like building a memmory bank. 

Find 1000+ puzzles, don't worry how fast or slow you solve them. Just get a board, get a clock, so you know there is pressure not to sit there and relax, then don't randomly move pieces. Think, then come up with as many lines as possible. TT doesn't really teach pattern recognition, I only think it's good to test your TT strength, which makes it very good.

This might help. http://www.chess.com/video/player/tackling-tactics-1200-1749

Ummm, so you're saying that TT isn't the most essential?

And justus, tyvm for the video

Do you get enough quality sleep? Tiredness can affect mental and physical capabilities.

Ah yes, because of school, I only get sometimes 6-8 hours of sleep

It's the "short period of time" thing that may be the problem. I do the tactics in two modes: (1) quick, intuitive, minimal calculation, and (2) slow, less intuitive, more calculation. My rating difference between the two modes is about 300 points.

Also, I think I get more long-term benefit out of slower, more mechanical/calculating study of problems.

TT is like your big book of chess puzzles, endless with the correct viriation. It's very good for quick thinking and to sharpen up and to test your strength, cause the puzzles ratings are determined by the chess commununity, but don't expect to learn 'How to mate a king on g7', just from doing TT puzzles daily, the puzzles do not go to theme although you might encounter famous problems and endgame problems. Chess tactical books that I like are, 1000 checkmate combinations, Susan Polgar's Chess Tactics for champions, and other books based on the theme and idea. 

A chess program called CT-ART 

http://www.chess.com/download/view/ct-art-30-demo 

This program si designed in theme, shows variations and when you do a mistake, points out the patern and shows refutations and side lines.