Do it longer. 20 minutes is just a settling in period. The more you do it the better you get.
Physical exercise first can help one mentally calm down quicker.
Finally, studying others methods is helpful. The book "the six dharma gates to the sublime" was helpful for me personally for jhana practices, and there are lots of other great resources and teachers available if you look.
Physical exercise first can help one mentally calm down quicker.
Finally, studying others methods is helpful. The book "the six dharma gates to the sublime" was helpful for me personally for jhana practices, and there are lots of other great resources and teachers available if you look.