Term or phrase that describes a person who feels more in control of a situation than they really are

I'm trying to find a way to describe a person who overestimates their ability for some situation.

For example, how would you describe a math student who thought they were proficient enough to pass a test without studying (but then fails).

Another school example would perhaps be a student who procrastinates and puts off a 3 week long project, only to scramble in the last few days. I'm not looking for the term procrastinator, as I feel like there is a term to describe such a person that would effectively lead them to procrastinate a lot.

A third example could be someone who has become fairly knowledgeable in computer security, but not necessarily an expert. This person decides to forego installation of antivirus, firewall, and security updates, thinking they can avoid malware by engaging in safe browsing and downloading habits. Said person would have failed to account for 0day attacks that perhaps security software could help mitigate.

So all in all, I'm looking for a term that describes someone who sort of over estimates their own abilities.

The closest thing I can think of is perhaps a charlatan, but that has a negative connotation. Additionally, I think charlatan refers more to a person who publicly proclaims their own false expertise, whereas the term I'm trying to find more or less describes a personality.

Self-assured (confident in one's own abilities or character) and overconfident seem like they would fit your needs.

Cocksure -- Presumptuously or arrogantly confident.

Also, feeling perfect assurance sometimes on inadequate grounds, from MW.