Concentration is a skill like anything else, and can be trained with practice. If you keep doing it often enough you will increase the amount of time yo can focus without thought. Going from one minute and thirty seconds to ten minutes can seem like a huge leap but if you do it in small steps it isn't as bad. You just need to do it a little longer each time and eventually you will get it. Though don't stress if you don't improve every single time, just keep at it.