Letter of poor attendance

Didn't even think I had terrible attendance but I'm now having an email saying they're watching my attendance record and further action will be taken if I don't up my game because this is a serious matter
What do I do?

Start attending everything I would assume.

^ This

Is there any particular reason why you haven't been attending?

For a week or so, depression from breakup but I still went in for most of them; once after that, I prioritised a deadline over a lecture. Today, I missed a seminar because I stayed up late, and now I'm giving that habit up for Lent. Beyond this, I don't know, but it's apparently serious now. Although my Learning Mentor says I shouldn't worry too much it';ll be protocol

Have you told them why you're missing classes? My lecturers are fine with non attendance if you notify them in advance, even if it's to finish an essay like you have admitted to doing. However if you miss several classes and don't bother to say why they will be on to you like a flash, and rightly so.