I used to work with an ex Olympian marathon runner.
He said wind sprints are the way to go to increase speed in general. I have never done them enough, so I am finally going to listen and try to put one of my run days dedicated to them,
Yeah, I too have a love hate relationship with tough work outs. So much easier if you have a partner to push you. Your ego gets involved etc so you try harder.
And you're right, afterwards you have a great sense of accomplishment.