Here is an instructive game that I played, opening with the Caro-Kann. This is the classical /spassky variation. The key moments of learning for me were 15… O-O? 16… Nxg4? and 24… Be5??
I understood that castling was likely bad as it invites white to attack on the kingside. There are some lines in the Caro-Kann where it is best to stay in the middle with the king or castle queenside.
I also knew that Nxg4 was likely bad as it opened up the file, giving it to white for an attack, but I wanted to see how it would pan out. With correct play white was in a winning position.
The last instructive move 24… Be5?? was a move I didn’t see as bad at all and it was a total blunder. I remember playing a game where I made the same mistake my opponent did, trading off pieces, rather than pinning with the rook and winning material.