To guard against complacency, what you say in the press conference and pre-match team talks must be taken into account. What you say and how you build up or down the next match can determine how complacent the players gets within the match. If you're having a good spell and have just won against a better opponent in the last match, it's important to say something about how tough the next match is going to be and that they needs to work hard to get an outcome. In situations where you are one goal up at half time, telling your squad in the half time team talk to 'Don't get complacement' could be the go-to option. However, if there are signs of complacency in their body language as the match progresses, you can use touchline shouts to reduce complacency. Personally, I would tell my players they aren't playing good enough and Demand More of them, or ask them to 'Focus' to ensure they can maintain a decent level of concentration.