"The clock and time management is a big part of the game, learning to leave your self enough time to win the game is a critical skill." I have no shame in flagging the opponent as they have traded a better position then what they would of had for time."
In rapid, the 1800 can plan a game and the 1300 can't, by and large. The 1300 tries all the time to win on time and so is incapable of improving. The 1800 is usually here to play chess and has more pride and understanding than to like winning on time. The main difference is the ability to plan and not to constantly blunder.
1800 rapid is 99.3 or 99.4 on chess.com I been as high as 1892 and consider myself a strong amateur player which I considered between 1800 - 2199
I have decent knowledge in all parts of the game but very incomplete, still get caught out often.