There at lots of things that unite human beings, particularly in the dark days after Christmas, when the daylight hours are still scarce, the holiday weight is lingering, and we haven't had a vegetable in what feels like decades.
We are all prone to bad days. Human beings love a breakdown. Take it from someone who has them on the regular, it's so important to surround yourself with a team of people that you trust to support you through the tough times. People that you know will love you extra on the days when you need it.
It can be so hard and complex to be in a relationship when mental health is at stake or worsening because you have a duty in your partnership to look after the other person as much as you can. Yes, it's important to have and communicate boundaries, but you shouldn't be in a relationship with a person you aren't willing to drop everything for and help.
Therefore, one important way that you can be there when your girlfriend is having a panic attack, or in the throngs of depression, or in anxious spirals – is to listen. Don't try to interject and reassure her with bland platitudes too early, just let her get things off her chest. Most things will be toxic and gratuitously angry, confused, and things that it takes saying out loud to realize that you don't actually mean. Talking can be a form of expressing things that you can then let exit you, and move on from.
It's horrible but far better than bottling up ugly thoughts
You will hear a lot of 'I hate myself', 'I can't do it anymore', or even 'I don't want to live anymore'. You have to try to think with perspective and kindness. These are ugly moments and ugly thoughts, but the person that you love is somewhere in the polemic of a bad day. You have to let them usher out the bad stuff. Be there and reassure her afterward that you are still there, and love her more than ever.
Indeed, just as she is there for you on your own bad days, it's so important that you establish a reciprocal relationship. Giving and taking in a relationship prevents it from becoming a one-sided relationship. You don't want a situation where one person is more invested than the other, or more willing to risk something, or more willing to go the extra mile for another person. This doesn't mean that you have extra money you are willing to spend, but instead that you are willing to make yourself vulnerable, and listen. Love people through their bad days, don't just smile with them on the good days.
Be willing to sit through ugly thoughts and insecurity
Help guide people through them with your love, attention, and patience, and be there to hold their hand and walk through it together.
It probably isn't the first bad day, nor will it be the last, but you can make them better. Or at least less bad. Any person in a loving and committed relationship will lunge at the chance to help their special someone. To prioritize them above everything else they had to do that day.
So invite yourself round if they seem to be struggling or growing distant. Absolutely make time for them if they reach out. It shouldn't be a burden, this is important.
She will be there for you, and has been, and you know it.
So please don't make it about yourself, and love her when she needs it most, on the bad days.