The context of the following conversation is Ash had lots on his agenda including a very important meeting he made a mental note of.:
Ash says I have this really important meeting I can't be late today.  I need to make a mental note of it..
The friend responds Why don't you put it in your calendar?.
Ash responds I did that too.  It'll send reminders to my phone..
The friend responds It's better if you just remember to do it on your own..
Ash responds Exactly. Technology has failed me in the past..
The friend responds Nothing's better than trusting yourself..