Is tension headache curable? Does it just keep coming back?

Possibly. Individual episodes may be cured, but nature of your work/lifestyle may cause them to recur: working over a desk/keyboard fatigues neck & shoulder muscles (mm); periodic breaks to stretch those mm with range of motion exercises can help prevent headaches. Moist heat to neck helps also. Otc anti-inflammatories (aleve/advil/etc) can reduce pain & inflammation. Therapeutic massage works well, too.