my Lego is full
Referring to the limited number of pegs to attach other Legos. People, like Legos, usually have a limited capacity for relationships. Some are four-peg Legos, some are 32.

We often fill our lives with meaningful relationships - people, or activities - and once our Lego is full, we can no longer add more.
My wife would love to have more kids, but my Lego is full. I don't think I could handle that right now.