[Celyn]

It's entirely possible to be close friends with someone of the opposite gender, even if they are dating someone else. He might be dating or preparing to date someone, but you'll still be his close friend. Even if there is a small decrease in contact (which can be natural in the early days of dating), you'll still be close friends.

I think it's also natural to find feelings confusing, as in, this person clearly means a lot to you and is a close friend, and though you don't feel ready to date, he would be your first choice. It's like the lines are blurred between good friends and a potential date, and this can make feelings complicated when the other person dates someone else.

Ideally, I'd like to say that he isn't going to abandon you, but obviously we don't know that for sure. But you have to have faith and trust in yourself that even if, worst case scenario, he did, you would still get through it. Even though it would be very painful and upsetting, you would pull through. It might also help, even if it's difficult, to try to stop self-sabotaging. When we worry about others abandoning us and engage in self-sabotaging behaviour, we may end up pushing the person away without realising it. We may then feel that we were right all along and that the person did abandon us. It's a bit like a self-fulfilling prophecy in a sense that we thought would happen, did happen, but perhaps we had some influence over that too.

If there is one particular girl that you seem to be preoccupied about your friend dating, perhaps you can unfollow posts that she is in? It might help in the short run.

It's not immature behaviour- you have your feelings and naturally it would be difficult to accept that a close friend may date someone else, and worry about them becoming disinterested in you. Try not to tell yourself what you 'should' be feeling, though it's okay to remind yourself that he has the right to date whoever he wants.

If he is understanding, then you could try talking to him about your fears. He might be able to reassure you, which is something you can try to remember whenever you are worried about him abandoning you. And if he does date, then try to remember that a relationship may take the front seat for a while, but he is still going to need his friends in his life. So keep treating him like a good friend and try not to self-sabotage.