When is it over-giving and when is it unconditional love?

I have a pattern of over-giving in my friendships. How can I tell the difference between being co-dependent/ over-giving and loving someone no matter what (as advised here in SCS and by Brooke).

I have a friend who has reached out a lot recently for support and I thought I was being loving to her by offering her the support she needed. What she needed was not particularly inconvenient for me i.e. contacts for various services etc. but then last night she needed emotional support which felt like too much, I said “I’m really trying to focus on more positive thoughts right now, I don’t think this is healthy to keep talking about how unhappy we are” as her venting about her partner felt unproductive (it was all stuff she’s said before). She then asked me to help her with something practical. I agreed to it and appeared enthusiastic, but this morning realised that I’ve gone over my limit again and don’t want to do it.

I tend to withdraw from people as it all becomes too much, so I say I’m busy then resurface when I’ve had a chance to tend to my own self-care. I’m struggling with loving the other person and taking care of my own needs. I also notice I feel resentful when the person doesn’t meet my needs back – like with this friend – she doesn’t help me out with practical things or listen to me re my partner, but that is her choice. I’m resentful because I don’t have the same ability to take care of myself.

I think in the end this leads me to invest more in friendships that are co-dependent so I don’t have to feel this resentment when the other person doesn’t give back in the way I expect. But I would like to have healthier relationships that are based upon us both being emotional adults. I guess I am confused about how to unconditionally love both myself and the other person. I’m afraid of losing people if I stop being there for them when they need me, but I’m wondering if this fear is what’s keeping me in this pattern and if it would actually be ok to lose people who don’t want to support me in loving myself.