title: ggplot: text printed by geom_text is not clear
body: <p>The text printed using geom_text is not very clear. How can I make it more clear? </p>
  
  <pre><code>data = data.frame(rnorm(1000))
  colnames(data) = "numOfX"
  m &lt;- ggplot(data, aes(x=numOfX))
  m + geom_histogram(colour = "blue", fill = "white", binwidth = 0.5) +
    annotate("segment", x=10,xend=10,y=20,yend=0,arrow=arrow(), color="blue") +
    geom_text(aes(10, 30, label="Observed \n value"), color = "blue") 
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/UbTjT.png" alt="enter image description here"></p>