$("#my-form").validate({
        invalidHandler: function (event, validator) {
            // 'this' refers to the form
            var errors = validator.numberOfInvalids();
            if (errors) {
                $(this).addClass("error");
            } else {
                $(this).removeClass("error");
            }
        },
});

validate = function(){
    $("#myForm").valid();
};

resetForm = function(){
    var form = $("#myForm").validate();
    form.resetForm();
};

<input type="button" onclick="validate()" value="Validate"></input>
<input type="button" onclick="resetForm()" value="Reset Form"></input>

$('#reset').on('click', function () {
    var form = $("#myForm");
        form.validate().resetForm();
});

<input type="submit" id="validate" value="Validate" />
<input type="button" id="reset" value="Reset Form" />

var errors = validator.numberOfInvalids();
if (errors) {
    $(this).addClass("form-error");
} else {
    // this will never be called because invalidHandler
    // is never called when there are no form errors
    //$(this).removeClass("form-error");
}

$(document).ready(function () {

    $("#myForm").validate({
        // your rules & options
    });

    $('#reset').on('click', function () {
        var form = $("#myForm");
            form.validate().resetForm();    // reset validation on form
            form.removeClass("form-error"); // remove error class from form
    });

});