Create a list of reasons that a partner/ loved one might not be able to get back to you as quickly as you'd like that have nothing to do with the health of your relationship (e.g. stuck in traffic, work ran overtime, depression, knowing they get overwhelmed sometimes, needing some me time, family emergency. Add specific reasons you might know for specific loved ones). Any time you get anxious when someone is uncontactable you can read through the list to remind yourself it's probably not a sign the relationship is falling apart! You might want to also write other soothing statements such as 'My relationships don't define my worth', 'I am loved' 'I am lovable' 'I bring so many positive qualities to the table, people are lucky to have me'.
Make a list of meaningful compliments your partner or loved ones have given you (or even stick in old cards or letters) so that when people can't be there for whatever reason you can remember they do love you.
Make a list of self soothing activities (check my self soothing story highlight for inspo). You might also want to add a list of your favourite feel good movies/ music/ books. Then if you are activated and don't know what to do with yourself, you can go to your list and pick a self care activity.
Also having notes like these saved on your phone can be lifechanging - it's so helpful to have the resources available at all times so that even when you feel overwhelmed your reasoning brain is still there for you!