How to use post-game analysis correctly?

Hi guys,

The title says it all: how to use post-game analysis correctly?

Longer explanation: I am using several methods to try to improve myself, namely:
- Studying tactics (doing puzzles almost everyday)
- Studying books (recently finished Silman's "How to reassess your chess"
- Doing post-game analysis of all my games, especially losses.

However, I am struggling with the last point: basically, I go through every mistake of mine with the engine, however very often I don't understand why the engine suggests a certain move over mine (I'm talking about positional moves, not missing tactics). Any suggestion on how to improve this? Is hiring a coach the only way for this?

A bit of background on me: I normally play 3 different formats,
- Rapid (usually 15|10) is the one I care most, as it allows me to have a live game but with still enough time to think the moves. However, I have been stuck for a while in the 1600s (briefly crossed 1700, before being pushed back)
- Blitz (usually 5|5) whose rate I don't really care, since I mainly use this format for improving the memorization of opening variations.
- Daily (1/3 days), which is nice for playing calmly and analyzing every position carefully.

Thank you for any suggestions!