There are a few tell-tale signs that you may be tilted.
First, you may find yourself making more impulsive decisions than usual. This can manifest in a number of ways, such as going all in on a hand when you wouldn't normally, chasing draws that are unlikely to hit, or betting wildly without any regard for pot odds.
Secondly, you may start to feel emotional while playing. This could look like getting angry at bad beats, feeling regret after losing pots, or celebrating wins too enthusiastically.
Thirdly, your play may become more erratic and less consistent. You might make mistakes that you wouldn't normally make, such as misreading hands or forgetting what cards have been played.
If you notice any of these signs in yourself during a session, it's likely that you're tilted and should take a break from the table to reset.