As someone who just resolved this problem myself, it needs to be handled in small steps. I just flew back into brushing multiple times and everytime I went back to nothing because I never properly integrated it into my day. I'd say start by finding 1 thing you do near a sink everyday, and keep your toothbrush near that sink. This reminds you everytime you pass it that you need to brush your teeth. Start with just once a day, always around the same time, always immediately after something you did near the sink so it becomes a routine. After that becomes something you don't have to actively think about doing, start integrating a second brushing at a different time. Once you no longer have to think about either time you brush your teeth, slowly adjust what time you do it until you arrive at the desired time.