Half-time team talks are essential to undertake If you haven’t already set a precedent that you’re more of a tactician and leave the motivation to the assistant manager (ie. Set the option in ‘manager preferences’ to ‘Assistant Manager handles team-talks).
If you fail to do a team-talk without this option set then the players will presume you’re extremely upset with their performance as you’ve failed to even enter the dressing room, in extreme circumstances (ie. You’re 5-0 down in a local derby) this might motivate them to try harder, however in most circumstances it will just ensure they aren’t particularly happy with you.