Self-review is nice, but please also bare in mind,
for some (not all) beginners, your reading and thought process
for each move can veer off quite quickly.
Example: if you spend 5 minutes pondering a move,
maybe the first 20-30 seconds, your reading is still 'reasonable';
but beyond that, it's mostly unreasonable. Of course, this is not true for everyone, but from my anecdotal experience with beginners,
this happens quite often. The net result is you waste 4.5 out of the 5 minutes.
On every move. Or many of the moves.
A very inefficient use of your time.
A much more efficient way is to think about it (but not so much time),
and find a (much) higher level person to help.
Again, this is not always possible.

For example, if you post a recent, 'serious' game here for review
(or any other venues), you may be surprised by your blind spots
that the reviewer(s) help point out for you.

It takes some experience, work, trial-and-error, and sometimes a good friend (teacher) to help us realize just how much (or little) we actually know.

See also DK effect.

I still don't know why I didn't invade the bottom right corner... or anywhere on the right side really.

- reading;
- small, slow moves (what you may say 'timid' moves);
- too fast/thin, overplays;
- all the basics (re: previous post).
- etc.

Suppose you make a move that's considered small or slow later in the review.
Well, there could be multiple reasons for you playing it.
Examples:
- there're no weak groups on the board, everything is OK; there are still big points left unclaimed, and you miss one (or more);
- your opponent has a weak group you should attack, but you don't notice it;
- you have a weak group but you don't notice it;
- there's a very nice sequence or tesuji that could gain you a lot, but you don't see it.
- etc.

You also mention fear of cuts. Again, this has multiple aspects.
Examples: knowledge of basic shapes; evaluation of current situation, etc.

See, it's all related. Our mistakes are the 'symptoms'; they reveal gaps in our Go knowledge.
Of course, each person's particular strengths and weaknesses are unique.
Generally, for your levels, it's the issues in the previous post.
For example, there's no one-size-fit-all magic pill (or solution)
to fix ALL your small, slow, timid moves.