I’m sorry to say that you might get a similar relapse again. It’s not like relapse A gives you one set of symptoms, then relapse B will be completely different. It could hit again in a repeat pattern.
But, now you are diagnosed, if you get painful spasms as part of a relapse, you can easily lay hands on drugs to take the pain away. Stiffness and spasms are controllable with straightforward drugs, such as Baclofen. If you start to get spasms,just see your GP and ask for some drugs to treat relapse symptoms (as well as perhaps steroids to bring the relapse to an end quicker).
You could even try to work on your anxiety by persuading your doctor to give you some (for eg) Baclofen, just in case. If you know you have a weapon to fight with, you won’t be so fearful of the beast.
Meanwhile, talk to your MS nurse and neurologist about disease modifying drugs (DMDs). If you can avoid relapses, then you won’t be anticipating such painful spasms as part of a relapse again.