You have something you'd really like to do, say you want to climb Mount Everest, you need a way to stay focused to train instead of getting on Tumblr for six hours a day.
Well you have some options.
Downloading an app or extension for you browser that limits your ability to visit certain sites. Personally I've downloaded Stay Focused for chrome. I immediately setup the nuclear option, AND turned on the thing that doesn't allow you to change your settings unless you can type in a message (over 420 characters) without making a mistake. Any mistakes and you have to start over. Caps, and punctuation count. Also you can't just copy and paste because it counts the number of characters you type in! It's pretty difficult, and I typed "The procrastinator is often remarkably optimistic about his ability to complete a task on a tight deadline;" about a million times because I'd only make mistakes after that point...
You have to enjoy your training! If you don't like it then why are you doing it? I understand that sometimes you don't have a choice, but if you're riding a bike as exercise when you hate riding a bike then find another option! If you just plain hate exercise then Everest is not for you, and I suggest you sit at home on Tumblr.
Maybe you just don't have the right tools at home in the right place for you to want, or be able, to do it? Put all your exercise equipment in one place, a place where you walk by often. That way you'll see the equipment and think "Oh hey I should use that". You're more likely to do it, at least at first, I promise.\
Another good idea is making it a habit. I've heard it takes anywhere from 2 weeks to 2 months to form a habit, so you're going to have to commit to it!
Some people might say "just do it", however, if you're as distractable as I am then that'll be hard for you! I'm great at remembering things like numbers, names, dates, dance routines, etc., but I'm so easily distracted that most things never get any attention, or at least not as much attention as it needs!