I don’t want to stir up a reaction against the word psychology.  What I mean is that your emotional state as a preacher can and will color your message.  Before you preach, take time to process any tension in any relationships, any frustrations with how your week has gone, any worries about what lies ahead, anything that might color your ministry.  A bad mood will subtly alter your delivery and energy.  A fearful heart will undermine your presentation.

It can only be a good habit to take time before preaching and pray.  Pray for the message.  Pray for the people.  But pray also for you.  Cast all your cares on Him, because He cares for you.  Cast them one by one specifically.  Express your heart to the One who knows you and loves you.  Process before you preach.  Preach prayerfully prepared.  Your soul/spirit/mind/mood/emotions, etc. will all influence your preaching, so be sure to bring it all under God’s influence first.

And if you have a headache, take a painkiller too!