How do I know that this feeling of loneliness won't last forever?

The way I see it, you won't find one perfect person to take away the loneliness forever. but you'll find people who take it away for a little time. Everyonce in a while, it'll go away, but then come back. And hey, when it does, learn to enjoy your own company. you'll find it to be one of the best in the world.

I've dealt with feeling lonely most of my life, and I know firsthand how infinite loneliness can feel. It can feel like no matter what I do, I will always feel lonely. I'm a list driven person; I'm always making lists to comfort myself. When I'm feeling lonely, it helps me to write a list of the people that I know for a fact love me. To take from Kevin Kantor, I start the list by listing myself (even if I don't feel love toward myself right now). That way, even when the list happens to be short, even if it's just me on there, I know there is at least one person that loves me. Take stock in who loves you, and reach out when you're feeling lonely. Eventually, you begin to realise that there are people out there who care about you, and the feeling goes away. You'll get through this. Remember that we are also people that care about you.

Because at the end of the tunnel theres always light, theres always a start of the tunnel and the end, and that end is when you will stop feeling lonely, your journey in that tunnel is your path on improving your mental health. That can be through seeking professional help such as therapy and counselling or even finding your self along the way and realising that you don't need anyone or anything to be happy. Once you have established that, that loneliness will go away on its own. Think of a past hurdle that you experienced and the fact that you got through that and got past it, shows how you could get through another hurdle that your are experiencing which is loneliness.