Powers Activate - Lower the activation energy to make it easier to do

One of the hardest things to do is get started, frequently many habits, activities and actions are easy to complete if you start them. If you can get on the tread mill for 30 seconds, you likely can go for 20 minutes, but it can be very hard to get on the treadmill. 

Similar issues can be found in writing, doing homework, or any task that mentally seems more onerous than it is. 

One of the best ways to get around this is making starting as easy as possible or as James Clear puts it well reduce the activation energy (usually by introducing a catalyst that makes it easier for you to start things). 

From http://jamesclear.com/chemistry-habits

You can do this in a number of different ways. BJ Fogg has a process called Tiny Habits where you focus on doing a small activity based on an easy trigger, like after you brush your teeth, promise to floss 1 tooth, an easy promise to keep and can get you started on your whole mouth.

Other things that make it easier - laying out your workout clothes the night before. Setting up a small gym right next to your bedroom so you don't have to go far. 

Setting up your workspace to minimize distractions. All these things make it easier to start the habit and for many that is half the battle.