Francesca Murphy was still in her school uniform when she was admitted to an adult mental health ward.
She was 18, still in school and extremely scared.
Mind Cymru said there were concerns about staff shortages, care planning and the use of restraints at mental health inpatient units across Wales.
The Welsh government said it had invested £2m for improvements.
Ms Murphy, now 27, said her life changed dramatically following a sailing accident in 2014.
She became trapped underneath her boat with a rope wrapped around her ankle after she capsized.
She was rescued and was physically fine, but it led to a rapid decline in her mental health, which led to self-harm and attempts to take her own life.
She was admitted to a child and adolescent inpatient unit but discharged back into the community the day before her 18th birthday.
Since then, she has spent time in various mental health inpatient units, voluntarily and under section, across Wales and England.
Ms Murphy, from Fishguard in Pembrokeshire, said: "I was what you would refer to as a revolving door patient."
She would go missing, before being picked up by police and temporarily admitted to hospital, before being discharged two days later.
"The circle would go round and round," she added.
Her longest time in hospital was between six and seven months.
Without the support she received from her psychotherapist she said she would not be here today.
However, she also said some of the experiences in hospital, where she was subjected to physical and pharmacological restraint, where traumatic.
She was restrained in a face down position at least twice.
Restraint or restrictive practice should always be a last resort and attempts should be made to calm volatile situations beforehand.
"[It was] horrific. I had three men and one female holding my four limbs and then injecting me and sedating me, prior to speaking to me to de-escalate the situation," she said.
"One time I remember, clearly I heard, ‘let’s just get her into the room’.
"I was still very much trying to overcome the memories of the sailing incident and when there was something around my ankle, it would trigger everything that happened.
"It would make me more unwell."
Ms Murphy agreed improvements were needed on mental health inpatient units.
She said consistency of care and clear communication was vital.
"If you’re going to say you’re going to do something, then do it. Do not say you’re going to put something in place and then not follow through.
"I was fortunate to have an incredible therapist who looked at me holistically, and they worked with my family… a lot of professionals wouldn’t talk to them," she said.
She also said there was a lack of eating disorder training in general psychiatric units.
Ms Murphy has now been discharged from mental health services and works two jobs, coaches sailing and has got back in the water.
"I want to speak up for the people who are no longer here to advocate."
She contributed to a new report by Mind Cymru that focuses on mental health inpatient wards in Wales.
Concerns were raised about staff shortages, a lack of data and general care and safety.
The charity found 13 of the 18 hospitals noted problems stemming from staff shortages in 2022-23 which negatively affected patients.
It also said more comprehensive data collection was needed to provide a fuller picture of inpatient care and restraint, particularly around race and other protected characteristics to tackle any inequality and discrimination.
It outlined several areas that needed improvement, including the need to bring restrictive practice legislation into line with the law in England.
Across the border, the Mental Health Units (Use of Force) Act 2018 - known as Seni's Law - aims to protect patients from disproportionate and inappropriate use of force.
In Wales, guidance is non-statutory.
Simon Jones, from Mind Cymru, said the guidance in Wales was similar but needed to be a legal requirement.
"The statutory element adds the legal safeguard and the data that’s collected is more transparent, so we want to see that in Wales so we’re really clear about what’s happening," he added.
The Welsh government said improving the safety and quality of mental health was a priority.
It said that was reflected in the £2m investment to drive improvements in services, which included a Mental Health Patient Safety Programme.
“We recently consulted on our draft Mental Health and Wellbeing Strategy which has been developed in collaboration with a range of partners, including service users and carers, setting our vision for improvements over the next 10 years,” it added.
If you, or someone you know, have been affected by mental health issues or self-harm, help and support is available on BBC Action Line