We've all had them and we all know how much of a pain they can be. After a stressful event, carrying groceries from your car, sleeping in a weird position, it can come full force and be a while before it goes away. Luckily, tension headaches, if that is what it truly is, are largely muscular in nature.
Your upper traps which connect to the back of your skull are largely responsible for tension headaches. In times of stress, people often store their stress and tension in their traps, which can translate into headaches. Mechanically, the traps will pull on the back of the head, and over time it can lead to a widespread headache. This also explains why after carrying heavy things people can also get symptoms: the force isn't being distributed in an optimal manner across the musculature of your shoulders/neck, leading to more tension going into the vertical fibers of your trapezius.
So what do we do? There are a few things. Stress management, for one, will be a big help if that is the root of the problem. Getting a routine, having a breathing practice, managing your time, having a good support group, etc., are all examples of good stress management. Massage can also help with this too. It can help manage stress and global tension by downregulating your nervous system using the variety of techniques at the therapist's disposal.
If it is more mechanical in nature, then that would involve having a better carrying technique and distributing force in a way that can better advantage the larger and more horizontal fibers of the upper traps, and just distribute force better throughout the body.
Tension headaches can make you irritable, less productive, more stressed, and make you feel like you can't achieve your daily routine as you would like. Your life should be full of energy and vigor, not limited by pain and discomfort. Take your days with stride and get in front of the problem before it gets in the way.
As always, if you suspect something more serious is happening, consult a physician or other health care provider. This is not medical advice and you should always go through a more thorough assessment with a qualified practitioner.