seˈcurity ˌblanket noun [countable]

1. a piece of material that a child likes to hold, to comfort himself or herself

2. something that you have had for a long time, and that you use to make yourself feel less anxious

[TahlilGaran] Dictionary of Contemporary English ▲

security blanket
something that one holds onto for reassurance or comfort (like a child and a blanket)
The boy uses his computer as a security blanket so that he does not have to go out and meet new people.

[TahlilGaran] English Idioms Dictionary ▲

security blanket
{n.}, {slang}, {colloquial} An idea, person, or object that one holds on to for psychological reassurance or comfort as infants usually hang on to the edge of a pillow, a towel, or a blanket.
Sue has gone to Aunt Mathilda for a chat; she is her security blanket.

[TahlilGaran] English Idioms Dictionary ▲