I think one of my big leaks in my tournament game is C-betting too much. If I raise preflop and see a flop with 1-2 players I'll C-bet almost 100% of the time. It's a habit that's extremely hard for me to break.
You should be rarely c-betting into multipl opponents.
For example if each player folds 40% of the time, the 2 players combined fold 0.4^2= 0.16 or 16% of the time.
A c-bet must work x/(x+y) % of the time to show an auto profit.
x being the size of the bet and y the size of the pot before the bet.
The smallest usual c-bet is 1/2 pot so 0.5/(0.5+1) = 0.33 or 33%
so against a single player who folds 40 % of the time a 1/2 pot c-bet shows a profit because it needs to work only 33% of the time.
However against 2 opponents with 40% fold rates their combined fold rate is 16% which is less than the 33% needed to show an auto profit.
Therefore you cannot bet into multiple opponents on just any flop with the plan of giving up if they call as it simply wont work often enough.
Hopefully that explaination will help you break this bad habit.