The water bottle of Berto

Ron was hurrying to his workplace. He could feel his heart beat fast and sweat flowing down his back. He had to make it to his office before 9 am. He knew he was stressed but he pushed himself to walk faster and reach on time.

When he reached his office, he was barely in time to sign in. He signed the attendance register and dragged his tired body to his table. Next to him was his friend and an elderly employee Mr. Berto.
Berto was a more relaxed person who never lost his cool. He would always be calm and relaxed. In fact, people joked that 'stress' was afraid of Berto.
Ron had a deadline coming up in 2 days. He was stressed and worried about it too. Ron needed help but he did not know what to do. So he turned to Berto and asked,"Tell me Berto, how do you remain so calm and relaxed?"
"Ha ha" laughed Berto. "I am relaxed because I do not give my focus & energy to every small problem" said Berto.
" What do you mean? Can you explain?" asked Ron.
" I mean to say that you can not go on worrying about every small problem at your office. I measure my stress handling capacity everyday. I never use my capacity fully. I choose which stress I need to take and not."
"What? I didn't understand.How do you measure your stress handling capacity?" asked Ron.
Berto smiled and pointed to a blue water bottle on his table. "I use a water bottle. Every morning I check whether I slept well, had a good breakfast, my mood etc and I know whether I am mentally ready for the day. If I feel I am fully ready for all the stress at the office, I fill my water bottle fully with water and come to the office. If I feel stressed and can only handle some more stress at the office, I bring a water bottle that is half full" explained Berto.
Ron wondered about this and said, "So you mean to say that you bring a water bottle that you fill depending on your stress handling capacity on that day?"
" Exactly!" exclaimed Berto.
" Ok. So how does this help in handling stress?" asked Ron.
"Well, I keep this bottle on my table. Whenever I feel stressed, I take a sip of water from the bottle. As the day progresses, I take sips of water depending on how often I am stressed. If I am about to finish my bottle, I realise that I have used up my mental capacity for stress handling for that day" said Berto.
"If I finish the water, then I do not take any more stress at work. Come what may. This way I do not take extra stress. I handle only what I can". Ron was amazed. Berto had found a way to measure stress handling capacity. This way, one could avoid being overworked and under excess stress.
Ron felt happy about this idea. He too wanted to measure his stress handling capacity everyday using a water bottle. By planning to change, he had taken the first step towards decreasing his stress.
When are you going to start?