How do you guys handle sombra/other flankers?

Hey all! I returned to overwatch like many of you recently and love the mobility of juno. I feel like i am able to give my team some good value but my main issue as Ive been put in better lobbies is I get very overwhelmed when being flanked. I typically try to place myself behind the team and use corners a lot so I am able to use speed boost effectively for countering ults and for better views when sending out torpedoes but it does leave me vulnerable to flanking.

I am usually able to handle a reaper since they are much slower than me and I can fly above their heads but when it comes to a sombra, tracer, anran, or vendetta I always end up losing a 1v1. I know its probably a skill issue and I get stressed out but is there a better way to handle this? Do you guys typically 1v1 flankers? Do you run away? Do you group up with your team? I get decision paralysis and just end up spamming all my speed abilities trying to get back to my team when I think the fight is lost but then I just get killed and it feels pretty embarrassing