Question about user login


I watched the tutorial. It seems the user keeps logged in when I use meteor account-ui. But when I use this code to login with my own ui:

if ( this.loginForm.valid ) {			
	(error) => {
		if ( error ) {
		} else {
			alert('login success');					
			this.router.navigate( ['/dashboard/home'] );

Then when I refresh the page and I check the Meteor.user(), it returns null. What is the best way to keep the user logged-in? Thanks.