Russia also has a legitimate concern about possibly unfriendly countries being right on their border. For example, the Baltic States now belong to NATO.
Back in the early 1960s the United States got all worked up about Soviet influence in our back yard (Cuba). And now we wonder why Russia feels the same about the Ukraine.
Yeah I bet Russia is worried about Estonia invading them. /s
No one is going to invade Russia. Russia will do all the invading.