Sentence:  When I think of the love my father never gave me I feel encased in a veil with steel threads. [...] Sometimes a happy thought can make me jump for joy, but I must be careful: if I jump too high, I'll bump into the veil. It doesn't hurt, but it always <WSD>tinges</WSD> my joy with sadness. 
Meaning of the word marked with <WSD> tags:  To affect or alter slightly, particularly due to the actual or metaphorical influence of some element or thing.