Bukkit

What version of the product are you using?
Spigot 1.8.3
lifestone 1.0.0

Do you have an error log of what happened?

[12:54:01] [Server thread/ERROR]: Plugin attempted to register task while disabled initializing Lifestones v1.0.0 (Is it up to date?)
org.bukkit.plugin.IllegalPluginAccessException: Plugin attempted to register task while disabled
    at org.bukkit.craftbukkit.v1_8_R2.scheduler.CraftScheduler.validate(CraftScheduler.java:400) ~[spigot-1.8.3.jar:git-Spigot-2ec6f06-7722428]
    at org.bukkit.craftbukkit.v1_8_R2.scheduler.CraftScheduler.runTaskTimerAsynchronously(CraftScheduler.java:141) ~[spigot-1.8.3.jar:git-Spigot-2ec6f06-7722428]
    at org.bukkit.craftbukkit.v1_8_R2.scheduler.CraftScheduler.scheduleAsyncRepeatingTask(CraftScheduler.java:137) ~[spigot-1.8.3.jar:git-Spigot-2ec6f06-7722428]
    at org.mcstats.Metrics.start(Metrics.java:237) ~[?:?]
    at com.cyprias.Lifestones.Lifestones.onLoad(Lifestones.java:45) ~[?:?]
    at org.bukkit.craftbukkit.v1_8_R2.CraftServer.loadPlugins(CraftServer.java:296) [spigot-1.8.3.jar:git-Spigot-2ec6f06-7722428]
    at net.minecraft.server.v1_8_R2.DedicatedServer.init(DedicatedServer.java:199) [spigot-1.8.3.jar:git-Spigot-2ec6f06-7722428]
    at net.minecraft.server.v1_8_R2.MinecraftServer.run(MinecraftServer.java:522) [spigot-1.8.3.jar:git-Spigot-2ec6f06-7722428]
    at java.lang.Thread.run(Thread.java:745) [?:1.8.0_40]