An estimate is not a commitment
Just make sure everyone understands what your estimate means. You aren’t committing to anything by telling someone how long you think something will take. You are just giving your best judgment about it.
One idea is to start giving your estimates as a range (from the most likely outcome to the worst case); ranges spark conversations most often than straight values. Another idea is to mention your estimate separate from your commitment: “I think it will take two days, so I can commit to having it in 3”. A third idea is just to stall when you aren’t ready to commit; ask for more time until you have an appropriate answer.