Time is a resource, use it!

Preambule

This blog attempts to improve on the blog
https://www.critmint-orchard.org/@/Variant_Enthusiast/blog/useful-tips-for-time-management/VQL3PJyL
that in my experience advises wrongly. I put an elaborate comment to that blog, but the author unfortunately deleted that.

Look at lost games

A chess game can end in 3 ways: you draw, win, or lose.
If you won a game, you might have done some things wrong, but those did not matter. Even if you find these out, you will not remember them.
If you drew a game, then there are 3 possibilities. You drew from a drawing, a losing, or winning position.
A draw from a drawing position just leads to the logical conclusion, nothing interesting.
A draw from a lost position can be treated as a win.
A draw from a won position can be treated as a loss.
That leaves lost games as interesting.

‘You may learn much more from a game you lose than from a game you win.’ – Capablanca

There are two ways to lose a game: lose on the board with time left on your clock, or lose on time.

Too fast or too slow?

If you lose on the board with time left on your clock, then you played too fast. Identify your decisive mistake. How much time did you spend on it? Would you have found the correct move if you had spent more time on it?

If you lost on time then there are 2 possibilities: either you lost on time in a winning or drawing position, or you lost on time in a losing position.

If you lost on time in a losing position, then you gave it your best effort. Identify your decisive mistake and work on that.

If you lost on time in a winning or drawing position, then you played too slowly. Identify the move that cost you most time. Was it a good move? Could you have found it faster?

Most play too fast; few play too slowly. Losses on time in winning or drawing positions are rare.

Fear of losing on time

Very common is for players to panic when time runs low. Do not look at the clock. Play at the right pace. Looking at the clock instead of the board is lost time. It may lead to irrational fear of losing on time and fear cripples your ability to think. You should only think about the position, not worry about possibly losing on time. Bullet players play 60 moves in 1 minute, but over the board classical players often panic when they have to complete 20 moves in 10 minutes. Moreover bullet players start from the initial position while the game phase short on time starts from a position you spent much time and thought on before.

You arrive at the right pace by feedback from your lost games.
If you lost on time in a winning or drawing position, then you played too slowly. Speed up by thinking less on the move that cost your most time.
If you lost on the board with time left on your clock, then you played too fast. Slow down by investing the leftover time to avoid your decisive mistake.

Spend time before move 30

A strong player in a recent blog advised in 90+30 classical to always keep 30 minutes at move 30 no matter what.
So this player basically handicaps himself in time to 60+30 as compare to his opponent’s 90+30.
When two equal players play, the one who thinks longer can look deeper and is more likely to achieve a winning position. Most chess games are essentially decided by move 30. The game may drag on to move 40 or 50, with the losing side trying in vain to avoid the inevitable. I recommend to use all time by move 30 and finish the game on increment. In any case try to spend more time than your opponent: it increases your chances of reaching a winning position.
A winning position low on time is better than a losing position with plenty of time left on your clock.

Openings

Bad advice: the opening phase should be played quickly. This is wrong: the opening should be played slowly and thoughtfully so as to reach a state of concentration and not blunder the first out of book move. Assume you know 10 moves of theory leading to a slight advantage for white. If you blitz out those 10 moves, then what do you do on move 11? Blitz as well as if by inertia? That move is then likely to be a blunder. Start a long think? That tells your opponent that you are out of book and warns him that the next move is your own and more likely to be wrong than the previous, theory moves.

Dorfman commented to white’s move 13 in this game:
https://www.chessgames.com/perl/chessgame?gid=1117973
‘My opponent had hardly used a few seconds on these opening moves, trying to add psychological pressure to the effect of his home preparation;
the result was the opposite, as it pushed me to concentrate to the extreme.'

Keres was one of the strongest players in the world and the author of a book on the Ruy Lopez. In this game with time control 2.5 h for 40 moves.
https://www.chessgames.com/perl/chessgame?gid=1072293
Keres thought about his 5th move for 2 hours. So Keres went down to 30 minutes on move 5.

Honfi was a strong theoretician. In this game of 2.5 h/40 moves time control he had used 5 minutes up to move 19 and Tal had used 90 minutes. Guess who won? In chess there is no time advantage, only board advantage.
https://www.chessgames.com/perl/chessgame?gid=1139797

Endings

How to make up for the time spent in the opening? By speeding up towards the endgame. This requires good endgame technique.
You will not be able to reinvent the Lucena or Philidor position over the board and even less when low on time.

An eyewitness told me an IM played blitz against Petrosian. They played with an analog clock, with a needle extending from the flag with a fine scale. Petrosian reached KBN vs. K with 10 seconds left. ‘So draw?’ asked the IM. Petrosian checkmated him within 10 seconds.

Calculation

Bad advice: "Briefly calculate the key lines. By the time your opponent moves, you’ll already know your response." Never calculate when the opponent has the move. You do not know which of say 3 candidate moves he will select, so 67% of your calculations are a waste of time and energy. As his move is not on the board, you have to calculate 1 move deeper than you should and you are more likely to err. You will get tired of constant calculating are are likely to err.

‘When my opponent’s clock is going I discuss general considerations in an internal dialogue with myself.
When my own clock is going I analyze concrete variations.’ - Botvinnik.

Other GM authors like Kotov and Krogius give the same advice: do not calculate when the opponent has the move.