<em>If you want to feel really well, you should get enough sleep. </em>This is a type of conditional sentence. It states a genreal fact, therefore the expected or general result is stated in the simple present " If you want..." and the condition to be applied is realised through the modal " you should ...", which states a piece of advice.
Has is used alongside the PRONOUNS <em>H</em><em>E</em> / <em>S</em><em>H</em><em>E</em> / <em>I</em><em>T</em> and <em>W</em><em>H</em><em>O</em> and SINGULAR NOUNS.