I don’t know how to be alone

I was only with my nex for 11 months, but in that time they managed to be the most affectionate, and then the coldest person I’ve ever met. I don’t know how to recover from receiving so much love and praise from someone, to being treated like I meant absolutely nothing. My mind and my body crave that level of validation constantly now, but I know I need to try and learn to be able to provide love to myself, and not need it from others. I haven’t been single for longer than a year for 6 years now, and have had three relationships during that time. How do I be okay with being alone? How do I grow into a person who doesn’t need to seek out romantic partners constantly? I want to be happy and fulfilled as an individual, but I feel so much pressure within myself, as well as pressure socially, to be in a stable relationship. Does anyone have any advice?