It can be both, as long as you stay clear about what it is. As a thinking partner it is useful. You can talk through a decision, rehearse a hard conversation, or ask it to challenge your plan.
It does not know you the way a colleague or friend does, it tends to agree with you, and it can sound confident while being wrong. A few guardrails help. Ask it directly to disagree or list the weak points in your thinking. Avoid sharing confidential or sensitive personal details. Keep real people involved in decisions about health, money and relationships. If you notice you are using it to avoid human conversations, step back. Review the privacy and memory settings in your account.