I think this guy on chess dojo is on to something important (see link) and I've been hearing about this for years, but have not done it.
How does anyone find improvements in their own game if they don't know what the improvements look like? How can one trust their own analysis is correct, and not just another mediocre set of moves?
First, one may use a computer to check not only for clear tactical errors but also
for tactical possibilities that one has overlooked. Every human overlooks some.
Second, a computer is less helpful (and trustworthy) about such important matters
as forming a good strategic plan. I would add that a plan also should take into
account the opponent's strengths and weaknesses and other competitive factors.
For example, in a blitz game I likely would not choose a plan where I hope to win
by converting a small advantage in the endgame because I would not expect to
have enough time to play a non-trivial endgame very well.
Third, there's a major difference between 'theoretically losing' and 'practically losing'.
Sometimes a student will ask me at which point of the game was he losing.
I may say that, yes, in this position you were not yet 'theoretically losing' because
if you could play tactically perfect defense (like a top computer), you would not lose.
But you already were practically losing because the position was too difficult for you to hold.
So you really need honest advice from a stronger player, perhaps a coach.
Can you get honest advice from a stronger player who's not coaching you?
Sometimes an older player will take the time to help guide a younger player.
In some chess clubs (with more or closed competitive pools), there's a factor of self-interest.
I can recall someone offering to help me until he began to feel that I was a threat
to defeat him, at which point he stopped offering. I accepted that.
What's worse is someone offering misleading advice that sets back a promising player's improvement.
I can recall an average club player who was very loud and dogmatic in 'teaching' young players.
Unfortunately, much of what he taught them was misleading or simply wrong.
I felt sorry for the young players who would have to unlearn much of what he taught them.
I am sure that he was not intentionally giving bad instruction, but there are a few malicious people who would.