1 - think and take your time

As you probably knew and as mentioned before, is disastrous. Having your cutting stones captured in a ladder is a major tactical error. There's no point in learning direction of play if you spoil the game this way. In this case, the ladder is very close, so it should have been easy to calculate it. So, I guess you didn't really calculated anything and just cut by instinct. Hence, my first advice is: "in fights, take time to read". This generalizes into "don't play without thinking" or positively stated "think about every move, compute a few alternatives, read a few moves deep".

If the game is played in real life, you can sit on your hands instead of holding a stone. If online, you can sit on your hands instead of holding the mouse. Maybe the game was blitz? Then my recommendation is to stop playing blitz games and go for time settings that allow you to think.

2 - count and fight

After the game was played out without any visible attempt to come back into the game. White kept a comfortable advantage of 10-20 points. So it seems as if you were either unaware of the score, or you were aware but didn't have the spirit to do something about it. In the first case, take time to count the score. You can do this by visualizing the borders of territories and count the points inside, or by roughly assessing in multiples of 5, or even more roughly by comparing territories on both sides. Even by the latter method, you would have noticed that White was ahead by a major amount.

Maybe you knew this, but then why did you not make an attempt to get back into the game by fighting? Were you waiting for the opponent to blunder? Or did you hope to gradually come back, point by point? In short: what was your strategy after ?