def send_email(request):

try:
    send_mail('Book request', 'email body', settings.EMAIL_HOST_USER, ['xyz@gmail.com'], fail_silently=False)

    #this message is not getting displayed in the same html page
    messages.add_message(request, messages.SUCCESS, 'Email sent successfully.')

except EmailMessage:
    messages.add_message(request, messages.SUCCESS, 'Error has occurred')

......
  rest of the code....

  {% if messages %}
    <ul class="messages">
        {% for message in messages %}
            <li{% if message.tags %} class="{{ message.tags }}"{% endif %}>{{ message }}</li>
        {% endfor %}
    </ul>
  {% endif %}

{% endblock %}