Post wel maar veranderd niks in de DB

<?php
ini_set('display_errors', 1); 
  include("dbconnect.php");
  
isAdmin();
CheckLogin();
if(isset($_POST['submit']))
{
  
    $id         = $_SESSION['id'];
    $username   = $_SESSION['myusername'];
    $naam       = $_POST['naam'];
    $anaam      = $_POST['anaam'];
    $woonplaats = $_POST['woonplaats'];
    $games      = $_POST['games'];
    $msn        = $_POST['msn'];
    $favgame    = $_POST['favgame'];
    $favgun     = $_POST['favgun'];
    $favgungame = $_POST['favgungame'];
    $manu       = $_POST['manu'];
    $info       = $_POST['info'];
    $avatar     = $_POST['avatar'];
    $pro        = $_POST['pro'];
    $rmem       = $_POST['rmem'];
    $hdd        = $_POST['hdd'];
    $vcard      = $_POST['vcard'];
    $scard      = $_POST['scard'];
    $shp        = $_POST['shp'];
    $mou        = $_POST['mou'];
    $keyb       = $_POST['keyb'];
    $opsys      = $_POST['opsys'];
    $info       = $_POST['info'];
    $avatar     = $_POST['avatar'];
  
        $update = mysql_query("UPDATE accounts SET
        naam             =         '".$naam."',
        anaam            =         '".$anaam."',
        woonplaats       =         '".$woonplaats."',
        msn              =         '".$msn."',
        games            =         '".$games."',
        favgame          =         '".$favgame."',
        favgun           =         '".$favgun."',
        manu             =         '".$manu."',
        pro              =         '".$pro."',
        rmem             =         '".$rmem."',
        hdd              =         '".$hdd."',
        info             =         '".$info."',
        avatar           =         '".$avatar."',
        vcard            =         '".$vcard."',
        scard            =         '".$scard."',
        shp              =         '".$shp."',
        mou              =         '".$mou."',
        info             =         '".$info."',
        avatar           =         '".$avatar."',
        keyb             =         '".$keyb."',
        opsys            =         '".$opsys."'
        WHERE 'username' = '".$_SESSION['myusername']."'") or die (mysql_error());
        if(!$update){
            echo "er is een fout opgetreden!";
        }else{
            echo "Gegevens zijn correct toegevoegd";
        }
}
if(!isset($_POST['submit']))
{
$select = mysql_query ("SELECT * FROM accounts WHERE username = '".$_SESSION['myusername']."'");
$data = mysql_fetch_assoc($select);
   }   
?>