Baseless fears/worries/anxieties have their spiritual source in Satan because of Adam's Original Sin which all his descendants have inherited or are born with.(GENESIS.3:14-16, JOHN.8:44, MATTHEW.16:23 & 23:27, MARK.7:21, 1JOHN.3:8) Similarly for sinful/satanic/immoral/evil thoughts of anger, hate, jealousy, greed, selfishness, lust, pride, doubts, etc that sometimes arise in our hearts.
....... When acted upon, sinful/evil thoughts in the heart will bear fruit into evil-deeds/sins, eg murder, adultery/sexual immorality, stealing, cheating/lying, blasphemy, insults, assaults and other offenses.
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Sin-in-the-heart = cursed by God with hell when people die = spiritual death.(ROMANS.5:12)
Sin-in-deeds = cursed by God with terror, calamities, etc = a sad and short life on earth.(DEUT.28:15, PROVERBS.1:25, 1CORINTHIANS.5:5 & 11:30, 1JOHN.5:16))
God gave people the Law(= His Law or Moses Law) to "save" them from the latter(DEUT.28:1; ACTS.15:24-29 = exemptions for Gentile Christians).
....... God gave people the Cross of Jesus Christ to save them from the former(JOHN.3:14-18).
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Your horrible anxieties(= from Satan) caused you to be like a ticking time-bomb in your relationships. Those affected/hurt may choose to avoid you, eg your future SIL.
....... You need to get a handle on your horrible anxieties, eg do not act upon your baseless anxieties/fears(MATTHEW.4:1-11, EPH.6:16-17), recognize baseless anxieties as from Satan, meditate on your anxieties(= accept the anxious thoughts and let the anxieties just come and go through your mind) or ignore the anxieties like ignoring Internet trolls or fake news, or etc.
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P S - OTOH, there are real anxieties experienced by stutterers(MARK.7:32), autistics, PTSD sufferers and other disabled people, work-related stress/anxieties, family-related stress/anxieties(eg sickness), etc.
....... There are healthy anxieties/fears, eg fear of being burned by fire, fear of God cursing/punishing those who disobey His Law, fear of the police and government, etc.