Jesus, undeterred, went right ahead and gave his charge: "God authorized
and commanded me to commission you: Go out and train everyone you meet,
far and near, in this way of life, marking them by baptism in the
threefold name: Father, Son, and Holy Spirit. Then instruct them in the
practice of all I have commanded you. I’ll be with you as you do this,
day after day after day, right up to the end of the age." Matthew 28:18-20 (TM-emphasis added)

I remember when I started traveling on my own for work. For years, my boss would always go along with me. He began by helping me with training, eventually he let me do most of it and just came for the company. He then moved on to other things. I missed the personal companionship but he had other people to train and I was ready to do it on my own.

The disciples had to be feeling some of the same fears, and Jesus spoke directly to them.
"I’ll be with you." The cool thing about God is that He is always with us. The in-dwelling Holy Spirit is ever present and active.

We are never alone.