The chain of command can release you if they think you're the wrong sort of person to be in the army. That's not the same as just not liking your job - it means that your CO believes that you're not good for the army.
Usually, this type of discharge is used for soldiers who:
- Question army orders and rules
- 'Refuse to soldier' (i.e. resist rules and orders)
- Encourage other soldiers to refuse to soldier
- Criticise the army in a way that leads other soldiers to criticise it
- Don't work well in a team
- Cause trouble in some other way
- Are unfit
This type of discharge is usually reserved for people who are a handful and more trouble to the army than they're worth - and who don't change after they've been punished - but it can also be used for people who are just not cut out for military life.