Britney Spears is shouting out her sons, wishing them a happy birthday month ... right after posting about how she had to cut people off for playing mind games.

The singer-songwriter hopped on Instagram Saturday to share several posts ... including a tribute to her two kids -- Jayden who turned 18 Thursday, though Brit will keep paying child support through November, and Sean who turned 19 today.

The mother-of-two says she hopes all their bday wishes come true ... and shared a few sweet photos from back in the day as well.

Seems the boys are still on their mom's good side ... which ain't the case for everyone -- 'cause right before she shared these pics for her kids, she shared a half-naked post with a caption all about the people she cut off this year.

Spears says she's reposting photos to her IG -- adding it's good for her self-esteem and self-awareness ... before firing off that fans wouldn't believe how many people she's cut off this year.

Britney says she's too sweet and naive ... and, she's allowed too many people to wreck her confidence in recent months.

She doesn't get into specifics about who's she talking about here ... but, we know she had a rocky end to her relationship with Paul Soliz -- putting him on blast for an interaction with paparazzi during which she felt used.

The two also got into a blowup fight at a Los Angeles hotel ... so, it wasn't exactly smooth sailing for the two -- and, it would make sense if Brit was talking about him.

Bottom line ... Britney's thinking lovingly about her kiddos -- and, she's got less warm and fuzzy feelings about others.