Age In Years = Minutes Of Meditation Daily

First we should try to understand the nature of human mind. Thoughts are the waves from the soul. Like the waves roar in the ocean all the time, thoughts also roar in the mind. If we try to resist when we meditate, surely they will persist. I experienced personally this truth. When I meditate the thoughts will rush more at the beginning, just I observe , unwanted thoughts will create resistance. I try to embrace them and accept them as they are.
Some times I was successful, some times not. That`s okay - I try to keep up.Some times all the thoughts subsidize and the breathing also very slow and in circadian rhythm.

Regarding the time span I do only 20 to 30 minutes at a stretch. We are not yogis to do very long meditation. I am a normal human being. I say to mind-some meditation is better than nothing. But forcing yourself to do for a long meditation is not a good idea, I think. Don`t worry about the time limit, just focus on your regular habit in doing the meditation.