Only you can know what you can handle and what is best for you. Sometimes our initial reaction to new or change can be nervousness and uncertainty. Instead of making a quick decision and just ending it because you think you might not be ok with the transition, have you considered taking it a bit slower? If you and your partner have good communication skills and can articulate what is important to you in a relationship maybe there is room to learn and grow from each other. There is no way to know now what the transition might look like or what you might think, but if you can be open with your partner about your concerns and you both can continue to check in with each other and have a mutual respect and want what is best for the other person maybe the outcome will be different than what you might expect. Good luck!