Tumblr Dashboard lets you use keyboard shortcuts to navigate, like posts

Tumblr has long allowed you to scroll forward and back through posts in your Dashboard using the J/K keys (shortcuts popularized by Gmail). Today, Tumblr has added the L key to let you like (or ‘heart’) the currently selected post.

Note that, upon logging into your Dashboard, you do not have a post selected. Hit J to select the first post at the top of your Dashboard.