Being in charge of your own treatment without the help of medical professionals is dangerous. You might be having contraindications and not even realize. I would advise you to see a doctor and explain your situation.

Sounds normal for some people and im sure your personal biology effects it. But yeah... That's typically what happens when you don't take stims. Withdrawal symptoms. I used to get that way by the end of the day when my Adderall wore off. It's sucked. In the end I just stopped taking it because it wasn't worth the rollercoaster ride of emotions. That irritability is what drives addiction. Be careful and tread lightly as you figure out the best usage.

In my case, in America, my doctor just kept increasing my dose... Which ended badly for me. Trust your gut feelings.

Maybe try a smaller dose?

That's common withdrawal symptoms for amphetamines (what Ritalin is). Taking more will obviously alleviate the effects short term but make you more dependant and worsen when you'll stop, and taking less will eventually run into tolerance and stop working.

For the immediate future I suggest to take less if you can manage, and to take other, lighter stimulants on your off days ( caffeine is the big one, also try simply exercising for an hour to let out all the frustration and produce dopamine on your own).