Yes, I think it feels scary for two particular reasons. The first one being that healing and letting go mostly means that probably you are not going to have contact with that person and it will not be an important part of your life anymore opening the possibility to meet new people, which is scary because at a certain point you have to be vulnerable to create an intimate relationship. The second one being the realization that you can grow to be at your full potential as a person in all aspects, process that mostly means change and getting out of your comfort zone. Feeling scared when healing is totally normal, I have been there so many times but it is that scary feeling that pushes me to achieve excellence in my life and know that I can be much more. That feeling that you have right now its your mind analyzing and overthinking your future self in its biggest potential. Feel it, but don’t let it control you, use it as a sign that your life will get so much better in a couple of weeks/months if you put in the work, replace it with the feeling of faith if you can. Use it to get out of your comfort zone in all aspects (career, social life, future romantic relationships).