Look at the sheet music, not your hands or the fret board.
Watch your tempo. If you are playing a song at 60 bpm in 4/4 time, this means that each beat gets 1 second. So don’t strum your chord four times real fast and then find yourself waiting for the measure to end. At 60 bpm you need to either strum four times with 1 second between strums, or depending on the melody, you could strum in eighth time; eight strums with 1/2 second between strums.
On a chord change, it’s better to miss the chord than to hit it too late. Hitting it too late throws off the rhythm of the song but if you just hold back because you couldn’t get your fingers there in time, hopefully all will still end well as your other instrumentalists (or vocalists) will carry the beat.
Simplify the real tough chords; even change them into a two-note chord if you have to. For example, you can play a Bb chord as x13xxx and just strike the A and D strings – this will sound just fine. As your playing improves, expand this into a three note chord (x133xx), and then finally try the full chord (113331).
Drop the slash notes on chords. For example G/B can be played as a simple G chord and the D/F# can be played as a D chord, etc.
If your fretting hand gets sore after one song, then you are probably gripping the neck incorrectly. The clamping pressure in your hand is provided by the thumb. The thumb’s position will vary from being wrapped around the top of the neck to sitting on the underside of the neck (in a pinching position) depending on the chord shape being played. Watch other guitarists and work on playing notes with the minimalist effort and force possible. If you play standing up, then you might also have to try a different guitar position by adjusting your strap length.
Don’t sight read; even if you know all the chords. You need to play through any song before you attempt to play it in a worship setting.
Keep your guitar in constant tune. Keep your strings clean and have them changed regularly.
Watch your tone. When practicing chords, play each string individually (while holding down the chord) and make sure that each string sounds clear and that it’s not muted or buzzing due to a misplaced finger. Every note, including the open strings need to sound bright and clear.
Keep going if you make a mistake because the song will keep moving on.