Indentation helps find structural issues

indentation-works.js

client.on('message', message => {
  if (!message.content.startsWith(prefix) || message.author.bot) return

  let user = message.mentions.users.first()
  const args = message.content.slice(prefix.length).split(/ +/)
  const command = args.shift().toLowerCase()

  if (command === 'marry') {
    if (!user) return

    const aEmbed = new Discord.MessageEmbed()
        .setColor(0xff0000)
        .setTitle('Error')
        .addField('You need to mention a user you dummy!')

    message.channel.send(aEmbed)
  } else {
    message.channel.send('You are now married to: ' + "<@" + user + ">")
  }
})