My girlfriend and I are planning to do shrooms for the first time, and want to know what can cause a bad trip

So we got our selves some caps from a good familiar source who said they were good. Planning to do a small doses, we were told to do 3 and are going to take 1 and then another a bit later during the trip if we feel like it. And we both have issues with anxiety sometimes, and so we are curious as to what can cause a bad trip or experience and even what might help if we were to go down that path.